Seeking ideas about speaker selection and placement

My rig is set up in a spare bedroom that is about 15' by 15' (somewhat irregular shape).  Most of my work is mixing stuff that was tracked elsewhere.  If I do any recording in that space, it is just a single instrument or sometimes several singers.
 
So my priority is on hearing the material accurately.  I have been using a pair of Yamaha MSP5 monitors.  These are very nice 2-way speakers with a 5" LF driver.  I think they are intended for near-field placement.  Mine are actually set on some shelves across the room.  The left one is 9 feet from my ears.  The right one is 10.5 feet from my ears.  That gives a stereo imbalance, but was necessary because of the doorway.
 
I'm looking to improve my monitor setup.  If I went with larger monitors, the only way to mount them symmetrically would be to fly them from the ceiling.  That may be a bit much at this stage.  I could get some floor stands to mount the MSP5s closer to my workstation.  That seems like the easiest way to make a quick improvement.
 
So my question really is, when using these smaller monitors, what is the ideal placement, distance from ears and separation left to right?  Any insights and opinions are welcome.

John's got the basics right. The MP5s are nice speakers - major studios will use them as their nearfields.  But you need to be closer to them if you are to get any sense of bass.   Ideally, your speakers and head form an isosceles triangle.
 

AT
But you need to be closer to them if you are to get any sense of bass.   Ideally, your speakers and head form an isosceles triangle.

Can you give me a rough idea of how close?  With my furniture arrangement, it would be easy to use floor stands such that each speaker would be about 35 degrees off center and about 3.5 feet from my ears. 
 
The only drawback to that is that if somebody else is working with me on a mix, they wouldn't be in a good place.  But I guess I could re-position the speakers a little in those cases.

I have tried many different speaker arrangements (distance wise).
I have tried the 3 triangle, ive tried the 5 - 3 spread triangle
But(and this is important) *The tests that I've done in my room, I have found that a 6 ft spread, at approx. 3.5 feet away works perfect. Not sure if anyone mentioned this yet...but the speakers are at ear height. 
My Control Room is 8 feet wide by 16 feet long. The spears are set up to travel the distance of the room, not the travel the width. I also have several sets of speakers for A/B comparisons.
My speakers are wired with Balanced cables (XLR) and each set is patched in to a 16 port patchbay.
This is so I can switch speakers out quickly for different listening environments. as well as Stereo, Mono.
 
Room treatment really helps as well. if I had to suggest anything to start with, it would be bass traps.
However, this is not always practical in a house, bedroom setting. so any good sound foam will do.
These need to be placed strategically.

Do have room for speaker stands? That could enable you to a) get the speakers closer to your ears, b) get them properly triangulated, and c) get them as far from walls as possible.
 
I'm not sure 8" woofers will really do that much for you. In a large room with acoustic treatments, yes. But in a mostly square room, deeper bass response is likely to compound your problems.

To reduce the reflections created by the window try something on the wall opposite that adds difraction so the sound doesn't keep bouncing from one to the other. A "live end/dead end" approach might be appropriate, where one side of the room, typically behind the listening spot, is left acoustically "live" and the opposite end of the room gets the damping. It's very much a matter of experimentation though.

One thing that might help quite a bit is getting the monitors to four or so feet from you and the same distance apart Nearfields are generally intended to be used close to the listener, and often really need to be at least a couple of feet from a wall either to their side or rear, otherwise the bass gets ramped up. Though that's more of an issue with larger speakers than 5". Setting up a position that works equally well across a wider listening area can be very difficult indeed. Speakers too far apart don't produce a wider "sweet spot" but a hole in the middle which makes hearing what's going on in the centre very difficult - which is one reason most live mixes are in mono. I'd be tempted to put your current nearfields close to the listening spot and a couple of 8" or so monitors further away, though if it's a choice between more speakers and killing obvious room reflection and reverb issues I'd go for sorting the room out a it first.

There's no need to spend huge amounts of money on commercially-made bass traps or other reflection-killing traps, much can be done using panels made of heavy grades of rockwool, especially if it's spaced a few inches off the wall so sound passes through it twice before it reaches the listening position. Traps place across corners often work better for taming bass than ones on the wall. The ceiling is also a good place to put traps, and probably isn't cluttered with other stuff. The door can be treated as well.

Bear in mind that many commercial audio tiles really only reduce high-freqency reverberations. A 2" thick acoustic tile might only be working in the 10KHz+ region. And diffraction is at least as useful as trapping and can massively reduce standing waves and flutter echoes.

Furniture and bookshelves make good absorbers/difractors.

This really isn't something that is easily answered on a forum because it's complicated. Try searching the web for "diy acoustic room treatment" and similar phrases.

Cactus Music
 
I think it's a waste of money to ad lib a room treatment.  

Say what who now ?

John
My comment is this. If you haven't done something silly with audio at some point then you haven't done anything with audio at all.

Best comment ive seen today.
that little saying can also be used in a lot of different ways....as in replace the word "Audio" and insert the word "Life"

As to speaker level mismatches - this can happen if one is being fed a balanced input and the other, an unbalanced input. Check your cables and connections.
 
Absolutely!! The minute you said this I went,, oh oh, bad connection somewhere. 
Or the audio interface is not outputting evenly Or the speaker is damaged. 
Run a diagnostic swapping. 
It helps if both cables are the same but it should not matter if they are both balanced and in good condition. 
I'm anal about cables so mine have to match 100%. 
 
Swap the cables at the interface. 
----If the the quiet speaker is now louder then it's the interface or the cable. 
      If it stays quiet then it's the speaker or the cable. Not the interface. 
Put the cables back where they were then:
Swap the cables at the speaker
----If the quiet speaker is now louder then its the cable.  
----If it stays quiet then it's the speaker. 
 
 If you rule out the Interface and the cables and one speaker being radically different in volume at the same settings,, I would be a little worried that it is damaged. I can see a small difference is possible but Yamaha is not a brand I can see having this issue unless it's damaged. 

With a little thought you could easily set up your system so that your speakers are fed with a balanced signal whilst still making use of your headphone amp.
 
This should reduce any noise in the system.
 
My setup is similar to yours and the routing is as follows.
 
In SONAR, my master buss feeds hardware outputs 1 & 2. These feed into my mixer and the main outs of the mixer go via balanced cables to my monitors
 
In SONAR, I set up a buss called Headphones. This buss feeds into hardware outputs 3 & 4. These feed into my headphone amp. You can connect what you want to the headphone amp outputs.
 
All of my other busses (Drums/Vocals.Guitars/Keys etc) all have a SEND to the headphone buss, so you can tailor what goes to the headphone amp by adjusting the send levels of each buss.

Good news