McIntosh MC275, enough power?

I'm contemplating an amp upgrade to the MC275 or 252 (ss) to drive my B&W 804s. Will also run a Rel Storm III sub. I love the sound of the 804s & 275 combination, but I am not able to bring it home for a demo.
At some other post somebody suggested the 275 might be underpowered for the size of my room and I might want to look into the 252. Room is 33' L x 15' W x 8' H.

I checked this SPL calculator
While it suggests the 275 would have enough power, I'm puzzled because it doesn't take into consideration room size.

Comments, thoughts, insights? All very welcomed!

BTW, side question: any issue with integrating tube amps and a SS-driven sub?

Go with your instinct. Get a 275, it will probably be fine, but if later on you'd like a little more headroom (control at higher volumes) then get another 275 and run them in mono. That way you can have your cake now, and more cake later if you want!
I have two Mac 275 version v. I am told that the newer models are more powerful then the older ones by 15-20 watts. With that said I listened to one in my system (only driving the top end of my Infinity RS1B's and then hooked up the second. I didn't see a major difference but I want to confirm that with only one Mac 275 driving the top it had enough power. I agree with Neil....go and try one.

P.S. Neil...I am beginning the tube rolling with Telefunfen's 12AX7's first.

Rick (RWD)