you have a tough room because the width and length are the same...I'd spend money on room treatments to tame reflections and stay with what you have it's decent gear. I would also provide a dedicated ciruit to the gear.
Your room is nearly a cube. That's going to give you some huge bass modes and holes. I'd spend a lot of time moving the speakers around (get rid of everything else in the room for a weekend). I had a room like that and ended up with the speakers firing diagonally across the room. Worked great for me. Room treatments might help too (I like RealTraps).
If you're committed to spending money on equipment, you'll get by far the biggest impact with different speakers. Your CEC amp should have enough guts to work with a set of Magneplanar MMG's, less than $600 factory-direct. One major advantage of planars is the way they load up bass in a room. They are also much less picky about sidewall reflections. Nearfield listening with MMG's is really special. They are spectacularly "real" sounding. You can take advantage of the factory free 30 day trial to see for yourself.
The Maggies will need to be out from the walls a bit, which may make them non-starters for you. In my similarly small room, it was dedicated to music, so I could get away with it. Read up on the MMG's. Hard to get much better sound for less than a grand! Eventually you can add a sub, some MYE stands, and you'll be in high-end heaven!