Homemade bass traps! Especially with the sloped walls in such proximity, some good cheap 2x4 boxes with heavy duty fabric weave (such as old couch fabric) stretched over the frames and stuffed with audio foam works wonders for tuning a room. It's especially important for the sides of your listening area. If you built 4 of them, 2 for the back and 2 for the sides, you would be set and virtually reflection free. An old futon hung up behind your tv and speaker position would work really well too. If you deaden the room, you will really open up the sound of your gear.
Looks good and I bet it sounds even better. Nice work Nick!
Cheers, PHil