+1 @rick_n
The reflections are going to play havoc with the sound. I agree that before you start swapping out equipment, work on the seating position and try some makeshift acoustic treatments just to see where that takes the sound. Throw down a rug(s) in front of the speakers. Got a couple of book cases, put them in on the side walls where the 1st reflection point is. Put a few pillows in the corners. Extra sofa, put it on the back wall. You get the idea.
And just double check the speakers are hooked up correctly and not out of phase. The picture of the back of the amp shows the speaker connections are mirror imaged left to right. (The "+" connections are to the outside.)
Lastly, you mentioned moving the speakers around. Have you also played with the toe-in as well?
...just my 2 cents...
- Jeff