I just read through this thread.
I completely agree with all of Bucknekked's post; however, given that you seem to be stuck with the layout you currently have, I think treatments may be a valid option. You can do some options that are not too expensive like make a fake window on the wall to the left of your left speaker by mounting a curtain rod and a heavy drapery to help absorb the first reflection off of that wall. That will better balance it with the open space to the right of your right speaker. The other thing I would do is pull your sofa 2-3' out from the back wall. Generally having your ears close to a wall will amplify the bass (which may not be a problem since you don't have much) and result in reflections off the walls hitting your ears close to the same time as the sound coming straight from your speakers arrives. This tends to blurr the resolution of the speaker. The delay from the sound travelling round-trip to the wall behind you and back (at least 2 feet away and preferably 3') allows your mind to filter it out as a reflection rather than part of the actual signal. If nothing else, test this by putting a chair out in your room and seeing what difference in sound you can detect.
If you absolutely cannot pull the sofa out from the wall, then using some sort of sound absorbent material (like the heavy drapery) on the wall behind you will help reducer the effect of this reflection.
However, the advice you have here is solid. I say get a subwoofer first and see what that does for your speakers. Then comes speakers.
Also, as advised, don't put money into electronics unless what you have is broken. I won't say that there is no way you would ever hear a difference if you changed electronics, but I will say that among major brands they are well designed (and have been for the last 50 years!).
The potential for improving your sound through electronics is minimal compared to changing speakers! Every speaker designer will tell you that they are forced to go through a series of compromises in sound quality to end up with their final product (at least among their peers). For example a 2-way speaker has the disadvantage of having the crossover (almost always a source of some discontinuity in the FR) in the frequency range that our hearing is most sensitive (so requires an excellent crossover to be accurate). On the other hand, a three way has the issue of costing a good deal more (assuming the same quality of drivers) and adds a second crossover. Ultimately the difference between speakers is huge compared to the difference between electronics.
I would not look at electronics until I had listened to many many speakers and was convinced that I had the speakers I liked best ... and even then I would not look at electronics unless I had money to burn!
