When it comes to a sub, if your budget allows, I'd second Wid's recommendation of an EP600 or EP500. I have the 500 and am very pleased with it. The 500 would suffice in a room your size, but that doesn't mean the 600 would be overkill. If either of those bust the bank, you might check out SVS, or HSU, or Rocket, or Outlaw. They all make competent subwoofers.

Jack

"People generally quarrel because they cannot argue." - G. K. Chesterton