Hi, everyone! This year, my church is having a Christmas party and last year this same time, we were able to hire out a guy we know really well who does an excellent job with live mixing and studio recording. Sadly, this year our budget was only enough to go to a guy who doesn't really seem to meet my standards.
In my church I'm the recording guy (no one else does it at all!!) and I'm not even that good at all, and though I've done very little live mixing, I'm somewhat becoming fed up with the fact that we're shelling out hundreds of dollars a year on something we could learn/do on our own that would pay for itself within 2 years.
 
So post-rant, I'm wondering what a decent, low-cost ($500?) stage system would run? Let's suggest that we already own enough microphones and we'll only need a desktop mixer and a pair of speakers? Better yet, what is a good pair of speakers (JBL)?

I'll be blunt with you,  the words "decent" and "$500" do not go in the same sentence together when it comes to PA.
 
I'm not saying you can't pick up something second hand that would do the job for that price, but it won't be the quality you're expecting.
 
If you can be a little more specific about your needs (number of channels, type of instruments, room/audience size, expected PA size, etc) then I can give you a list of what you need that you can pick from.

Alright- we'll need to be able to input in 3 channels at once: 2 XLR's and one of either line-in/RCA, 3.5mm or 1/4in. Like I mentioned in the first post, we actually own some of the gear already. We basically only need a pair of speakers (correct term?) and a small portable mixer. It's tough to give a space estimate... let's say 60ft x 40ft.
We're definitely going to be using mics and sound devices (players, laptops, etc), possibly digital keys, I wouldn't even bet on guitar/bass at all.
 
If possible, could we even think of JUST a pair of speakers? We might actually even be set in terms of a portable mixing setup.

When you say a set of speakers...  
 
You have 3 choices.
1) Passive speakers, an amp, a mixer.
2) Passive speakers, a powered mixer.
3) Powered speakers, a mixer.
 
From what you're describing I'd recommend a small powered mixer and a pair of speakers.  Don't forget you should have stands for the speakers for them to work efficiently.  If I point you in the right direction I'll leave it to you to choose exactly what you want based on your budget and your better knowledge of what you want it to do.
 
It would be very easy for me to say you need this, this and this and then you find its not loud enough or whatever.
 
Gimme 20 mins.

If you can get a mixer setup then something along the lines of these should do for you within your budget.  There are equivalents by Behringer which would be worth looking at, again within your budget.  Don't forget you'll need two, and just like studio monitors, these are mostly sold as singles.
 
As technical advice, in this price range go for a large speaker size 12" or 15".  The smaller sizes will not give you what you want and are only real any good for one-man-band pub singers and bingo callers. The bigger size will move more air without requiring large movement and thus cheaper to make.   My Powered PA uses 8" drivers, but they were $1500 each...  (the cabs)  and I still want some subs..
 
An alternative (just within budget) would be a split set like these which includes built in mixing.  Again you'd need two to link together, but you save on speaker stands and a mixer...  you can buy the top unit separate without the sub, but I wouldn't recommend it for the reasons I gave above.
 
Once you start moving into the bigger names the prices leap up to match.
 
 
Edit to add:  I tried to pick examples available in US, and the prices shown are current sale prices but are indicative of what this stuff costs.

I'm curious about the second option you posted- What actually does it imply, do you have to chain two together, then control volumes separately? Seems like a little more work 
 
So I'll be on the lookout for 12"-15". I'll definitely look for things I can try out at locations... Think I could find used ones that are bigger or better?
 
Thanks, Karyn!

You chain two together, yes, but it's easier than it sounds.  You just run a mic cable from one to the other, the line output on the one you've plugged your mics into is post master volume.  You just run the second on max and it follows the volume of the master.
 
If you need more you can keep adding more units.  If you think you've outgrown it, just add an external mixer and you have the start of a full blown PA setup.
 
It is a good system (the split sub, not that one in particular), because its easy to mix and match for different requirements and the biggest parts are the subs.
 
Shop around though if you can. There are several systems on the market at various price ranges. The main difference will be power and features until you start to spend serious money for the extra stuff, like digital networking....
 
Don't look at the Presonus SL series... they are way out of your price range..

http://www.sweetwater.com/store/detail/EON610
Don't know about the inputs on that, but reasonable price.
That is a Class D amp, new kind, I forget what that is all about, but since the wattage is so high, then I suppose that would be enough. See if a mixer plugs into that, and get a $100 mixer whatever, perhaps whatever anyone sells. Stands probably cost more, and all the cables and any of that stuff, which will add to the price. But there are other ones also. - 10dB down probably on low end and perhaps on high end. How much down, well, that maybe be a concern, if you like deep bass or really high highs that probably most people can not hear. But probably works fine, using mixer bass and treble control (or midrange) whatever.
 
12" speaker (one) with a mixer that puts out either mono or stereo (if you want another speaker later on. (no stand if angled on floor or with a stand for the speaker. (or the 15" speaker one but that to me be too much bass.)
??
 
http://www.sweetwater.com/shop/live-sound/pa-speakers/
Well, I suppose there is something there, I think you can figure it out.
Or at a local store, or ZZSounds whatever or Musician'sFriend or another one of those on-line places or at a local store GC whatever. Wherever they sell any of that PA stuff (musical stuffings).
 

Check out Alto speakers, they are powered and seem to get nothing but good reviews. No body seems to have issues with them. They are not super powerful but read the reviews and you'll soon get a feel for them. And they would be close to your budget. There's nothing at this price point I would recommend. I tried the "B" brand but they blew up after only a few gigs
http://www.altoproaudio.com/products/ts112a
 
I really want some Yamaha's or QSC but you can buy 2-3 of these for what those brands cost. 
I now have the Mackiesrm350 I picked up used for $250. 
https://www.gearslutz.com/board/reviews/884803-mackie-srm350.html#post9600729
 
but the sound quality is boring. 
So shopping around I came across the Alto's.  I want to try them first hand before I buy but every time I'm in a store they are sold out.? 
I use 12" speakers.  I have a Yamaha passive system served me well for 18 years now.
http://www.cactusmusic.ca/johns_rig.htm
 
And my latest trick , the pour mans sub. I just sold my Yorkville 18" powered sub , too big for my Subaru. I'm using a 200 watt Bass amp. Works fine. Just turn the Mid and Treble off and the Bass up to 11. 
Looking into the price of powered subs as compared to a bass amp, you sort of scratch your head. 
I'm looking to try a Fender Rumble 12" as my low end. 
 
Any how, I would see about the Alto 12". 
 
I also just bought a Mackie Mix 8 mixer for $ 65 Black friday sale.. it's cool. 

spacealf
http://www.sweetwater.com/store/detail/EON610
Don't know about the inputs on that, but reasonable price.
That is a Class D amp, new kind, I forget what that is all about, but since the wattage is so high, then I suppose that would be enough. See if a mixer plugs into that, and get a $100 mixer whatever, perhaps whatever anyone sells. Stands probably cost more, and all the cables and any of that stuff, which will add to the price. But there are other ones also. - 10dB down probably on low end and perhaps on high end. How much down, well, that maybe be a concern, if you like deep bass or really high highs that probably most people can not hear. But probably works fine, using mixer bass and treble control (or midrange) whatever.
 
12" speaker (one) with a mixer that puts out either mono or stereo (if you want another speaker later on. (no stand if angled on floor or with a stand for the speaker. (or the 15" speaker one but that to me be too much bass.)
??

Bare in mind that's an each price, not a pair.  And the lack of inputs would require an external mixer with related connecting cables. + stands,  you'd be looking at $1000+ for a working system.
 
Still good value, but double the budget.