Either VTF-3 or SVS will do the job. I have a VTF-3R and it's great. It looks nice and could double as an end table. The SVS units have lots of punch, though.
Another option would be using a 5.1 config and instead of rear surrounds get an EP500 or 600. I'm not a big fan of 7.1 from a price/performance standpoint. But some new movie soundtracks are now done in discrete 7.1. Some people like it.
But if you've already had the EP500 you know what that's like.
Acoustic treatment is very tricky. There are general rules, but so many uncertainties it's often hard to predict. Without an expert's analysis, I'd be conservative about spending money on acoustic treatment.
