Speaker placement and Furniture -assitance needed

Hello all - I have a 13 x 16 room or a 15 x 15 room, i would like to setup my stereo in one of these room but i also want it to function as a sitting room for myself and when i have guest, the room has no tv or video considerations, although i ususally prefer the long wall for speakers i must use the short wall fi i use the 13x16 room, i have eliminated the possiblity of using the 15x15 room due to its square shape, i been told rooms with equal dimensions are not good for sound for some reason or another and my experience seems to confirm this, my main questions are-
1> is there a way to counteract the acoustic effects of the 15x15 room using only the foam acoustical panels, i would prefer not to have them but will bass traps help?
2> if i use the other room it is necessary that i place two chairs in the "sound field", they will be approx. 6 to 7 feet from the front baffles and will be close to the the same distance apart as the speakers, approx 7' all furniture will be leather (its a cat hair issue)
3> what are some possible effects of placing a sofa or chairs between the speakrers?

Also, the one of the long walls has a arch way that is approx 7'X 7' and is closer to the speakers and is probably where the speakers would first reflect, the other side has a glass door and windows, approx 8' in the middle, i have think curtains up now but i can get thicker ones if needed - SPeakers cannot be more than three feet from the wall to the front baffle, sofa and forementioned chairs will be on the other side
I will experiment a little this weeked but as i have not purchase the furniture yet it is somewhat difficult (i only have the sofa and some cloth chairs i can try it with

I think it would help to know your equipment, specifically the speakers. Some speakers are much more flexible on how they can be placed than others.
Bass traps will help in any room and I consider them mandatory for good sound. You're correct that you don't want to use the square room. Bass modes are enough of a problem in a rectangular room. Foam isn't much good for low frequencies. Rigid fiberglass diy panel traps are easy and inexpensive to make if you don't care to buy them. Do a Google on room acoustics. It's the first step in getting good sound from any system no matter what someone spent on it. Bad acoustics equal bad sound no matter what gear it is.
You might want to consider a diagonal set up with the spearkers on each side of the corner if you want to use the 15x15 room. I have a basically square 17x17 room and I use this set up. It sounds pretty good with no acoustic treatment, although I plan on doing more with that at some point. I had a more common set up with the speakers on one wall, and I had a lot more problems. WIth the diagonal set up the sound is very good in my listening position with no trreatment (but watch out if you go into the corners when the bass is cranked up!).

I know a lot of speaker manufacturers such as Bobby at Merlin uses this set up for shows when they have a small square room. I think I'd get further benefit from bass traps and some acoustic panels at least for primary reflection points.
thanks for the response, my current system is a musical fidelity cd-pre and a pair of paradigm active monitors, this is temporary as i have been waiting to find the right space before purchasing a new system, i will primarily look for front-ported, acoustic suspension and other designs that work well near the wall, in the past i have gravitated toward floor standing designs