B&W 683 floor standers

I'd like to hear from those who own and play these on a regular basis. How do you like them overall? Are they too boomy at times? What size is your room? I'm considering them as an upgrade from B&W DM603-S3's. My room is moderate in size (2400 FT3) with 2 openings to hallways, no doors. What do you think? Do they produce good slam and punch at the low end? My room is bass starved and needs powerful speakers in this dept.