No matter what monitors you end up purchasing, you will have to learn them in the context of your space.  One thing you can do is bring reference material to your retailer and listen to different ones.  The ones that sound closest to what you think the reference material should sound like are probably going to be a good choice.

I can tell you a long story about studio monitors, PA speakers, home stereo and movie playback,, but I won't . It would take to long to type out and put everybody to sleep... ,I'll try and be breif
 
 My first monitors were Tannoy PBM 6.5's. They were liars but I got used to them. We blew the tweeters one day mixing too loud. We finished the album using a Panasonic Getto Blaster that had a line in and my Yamaha PA. This actually worked better that you would have thought thanks to the getto telling us when we had to much low end and the PA being more or less accurate enough. 
So next I bought the Yamaha NS10m's being a Yamaha dealer at the time. 
They were like night and day from the Tannoys and I became a happy mixer forever more. When they die I'll buy the new powered version HS 80m which seem to be the closest. 
 
After I shut down my commercial studio   I dragged all my stuff home and got the bright idea of using the NS10m's  for our home stereo. It was disappointing.  NS10m's won't lie to you at all, But they sort of suck as a home stereo. 
I have these Mission 701's that are awesome for music play back and one day I got the bright idea of using them for studio monitors,    It was disappointing. Missions 701 will lie to you and make all your music sound nice and full but they suck as studio monitors because your mixes will sound way off on other systems.  

And therein lies the difference and why awesome sounding studio monitors are not what you want, but accurate is.  I guess accurate is boring until you get used to it and settle in. 
It's totally two different worlds your in while mixing or listening to music. 
 
Ok I have my music playback and my studio listening experience under control. Then slowly the home stereo turns computer driven and all the CD, tape and mini disk gather dust. And the computer can play movies too. Hmm, what did they say?? I'm sorry but the dialog is quiet but the explosions and background music is deafening? The Mission 701 suck at movies.
 
I'm a Goodwill pack-rat. I find all these old school oddball speakers for $3.99. each. 
So now we play movies through this miss matched set of a Boston HD5, An RCA center channel beast and some cute little 5" Technics, all nice solid wooden boxes. and it works for movies but now the music sucks... 
 

You should read the first chapter of Marc Mozart's Your Mix Sucks. I'm posting this here, because it sent me on a mission to find an old, 1980's boom box. There's a few things to seriously consider when working with monitors, some ideas I agree with, while others, I don't.
 
1) Use as full-range a set of monitors as you can when critically listening. However, when making mixing decisions, especially around spacing, panning, levels, etc. use a cheap-o boom box at a very low volume. Get your mix sounding great there, first. Then bring up the mix on your high-end monitors.
 
2) Be sure you have a GOOD sub, if you need one. Those cheap, bundled subs you get with a sound-bar are not ideal, and I strongly encourage not using them. X-over the sub with your monitors as best you can. You should not be able to localize the sub.
 
3) Listen, listen, listen to pro mixes you like on your speakers that you use in your room, and at the level you intend to mix at, not the loud levels you want to dissect. Even if you are in your room listening, don't think you have to sit in one position. Walk around. Stand up behind your chair, on the floor, etc. Do other things than just listen. Let your sub-conscious mind listen. Eventually, it will become second nature to know what sounds good and what doesn't.
 
4) I do recommend testing your mixes on many systems, but not mixing on many systems. Get it right on a couple of of sets of speakers, not 10. But get it right on what you have. If it's not right, try different listening levels, or even better,
 
5) Pay a mixing engineer to sit in with you on a session and make some recommendations on your mix. He/she might be able to immediately offer some advice that will help you tons...no, I mean TONS!!
 
6) I use a set of 1st-Gen Mackie HR824's, a set I won at a Mackie d8b seminar, over a decade ago. I use them for nearly everything except integrity checks. I don't know if I would have bought them, if I were shopping, but they sound pretty good for their size (not totally flat, btw, as the pedigree states). I also do some listening on a set of Polk Audio SRS-SDA 2.3TL speakers powered by a Pass-X350. With that said, I just purchased an old 1980's Realistic boom box, which I am excited (for the first time ever) to listen to that piece of ______. But I know it will help my mixes!
 
Best of luck!
 
Footnote: Many would argue that the Yamaha NS-10 speakers (with tissue over the tweeters) were the original "truth" monitors. OMG, they sound terrible. Needless to say, I have a set of the NS-10 Studios. Even those sound pretty horrid. So, the best monitors may not tell the truth. Some crappy ones will be more honest, perhaps.

fireberd
I upgraded my studio monitors, about a year ago from Samson Resolv 6.5a to JBL LSR308's.  With the Samson's my mixes tended to have too much bass.  With the JBL's the problem is gone and I can get accurate and proper bass levels, along with an overall better mix.  The JBL's are $500 a pair (sometimes they can be found cheaper).   There are JBL LSR305's that are about $400 a pair. 
 
I went with the 8" model because of the bass problems I was having. 

+1 on the JBLs
 
However, room acoustics remain the 800 pound gorilla....

And do not forget, you do not have to buy new.
 
Craigslist is just one of many possible sources. Check the list for your price range.

I could not be happier with my Equator Audio D5's. I cannot believe how amazing they sound for the price. Very detailed and accurate. I think I paid $300 for the pair in a sale but they normally run at $400. It's worth getting isolation pads for them. But the most important part - if they're going to be in an untreated (or inadequately treated) room then invest in ARC2 as well! It will likely be the one of the most important gear purchases you make. The extent to which ARC2 improves the sound of your monitors is astounding. It's like night and day. In fact if the D5's and ARC2 falls within your budget then I would lean towards getting them both rather than spending the whole amount on a more expensive pair of monitors. You can always upgrade the monitors at a later date but you'll always have ARC2!

IMHO all monitors lie to you, even the best ones you can get. It's not necessarily the monitor that's going to make the sound, it's more what you're using for a reference. When I was doing live sound, I always had a copy of Skyscraper by David Lee Roth in the CD player. If I could get a PA sounding good playing that CD, I knew I would be able to get a great mix from the band. I called it David Lee Reference (Richard Kitchen). The same works for studio monitors, as long as you don't have garbage, if you have a reference, you can make a mix sound good. Yeah, the reference is going to sound different on different speakers but if you can get your mix sounding as good as your reference point, it's going to translate.
Relative to HS8s, Rokit 5s sound muddy, but if you listen to a reference track on either speaker, you can get an idea of what your mix is going to sound like. Regardless of what you use in the studio, it's not likely that anyone will be using the same speakers to listen to your music.
I guess the answer is, get the speaker that lets you hear the most detail and that allows you to hear the most variations from your reference. Only your ear is going to tell you what you really need.
Yeah, it's a crappy answer, sorry.
 

All great info here. I will echo that ARC 2 will compliment your room situation regardless of what level of treatment you can afford. The VLM box will compliment your headphone situation immensely for a small price.
 
Rocky

bluzdog
All great info here. I will echo that ARC 2 will compliment your room situation regardless of what level of treatment you can afford. The VLM box will compliment your headphone situation immensely for a small price.
 
Rocky

Correction: VRM Box. And yes they are great for when you have to work with headphones, or just checking how your mix translates to a variety of speaker and room types.

sharke

bluzdog
All great info here. I will echo that ARC 2 will compliment your room situation regardless of what level of treatment you can afford. The VLM box will compliment your headphone situation immensely for a small price.
 
Rocky

Correction: VRM Box. And yes they are great for when you have to work with headphones, or just checking how your mix translates to a variety of speaker and room types.

Oops! Thanks for the correction Sharke. It's a Focusrite VRM box (http://us.focusrite.com/usb-audio-interfaces/vrm-box). I have seen them on sale for as low as $50. I was working on a VLM (http://www.isddd.com/resources/vertical-lift-module-vlm-infographics) today and must have had a snickerlish mind fook.  I have a pair of Dynaudio BM5a's that I love http://www.soundonsound.com/sos/jun05/articles/dynaudiobm5.htm but they may be over budget.
Anywho, lots of good info here. All the best the op.
 
Rock