I think that the your Anthem will power the Sopra's just fine. I'm driving Sopra No2s with a Hegel H590 (300w/ side, dual mono) and it's never clipped or run out of headroom.
B&W vs. Focal: I disagree with some of the comments, I'm in the camp that the Sopra's will be nice step up sonically. It's a much more robust speaker, better crossovers, much more substantial cabinet (for better bass). The B&W weigh 73lbs the Sopra's are 120lbs.
Having said that, you have a very large listening space and it will be challenging for any speaker that size to fully pressurize it with bass. Subs are an obvious option or perhaps consider the larger Sopra No3. Good luck and cheers.