The idea is to have your front three very closely matched for their sonic character. It is not unreasonable for someone to be talking as they walk across from left to right or for a hoovercar to slowly glide by. In these cases you do not want the sound character to transition as it shifts from the left speaker to the center speaker and then to the right speaker. Consequently, it is preferred to have the center be of the same model/series as the L & R.
I don't remember, but I guess you had the Pioneer center. If so, I do believe the difference between the sounds will be fairly conspicuous!
So have you tried the DCM's yet?
For soundproofing the room, I'd suggest you start a new thread on that topic! But the best way I know of to soundproof a room involves using separate studs for the inside vs outside walls, and I'm thinking you are not interesting in tearing the sheet wall off and installing new studs and sheetrock!