We are now in to a subjective realm which can be dangerous.
First, my room is 23x20 and is 18' high--and open to the kitchen through two casement doors, and open on the other side to a loft, overlooking the room.
This amp will play very loudly, but I am almost certain that you can clip it. In fact, it can almost become a challenge, if your tastes run to loud, and rock, or bombastic music.
It is a real 150 watt into 8 ohms, doubling into 4, so 300 watts is considerable power, but not as powerful as the 450 watt VTL, which you can clip already.
I like it because it is as neutral as the tubes you chose for the pre stage, and is very clear without being the least bit harsh.
Aren't the Carvers the ribbon design, if memory serves?