I've got the 350 in a 20'x15' room open on one side. I use it 80% movies, 20% music and I've got to say I love it.
There are however two things you need to know about me.
1) Unlike most I have no desire to hear timbers moaning when I crank up the sub. I just want a nice rumble without it trying to destroy the house.
2) Unlike almost everyone else I am very content with the 350 and feel absolutely no need at all to ungrade. Thats also the same way I feel about my 60s. ....sorry Axiom
good luck with your decision.