Are you using the Sound Anchor bases and have you tried to move your 7B’s back a little to the wall? I use a Pass X250 with Wywires cables with Alex’s biwire jumpers with the + lead of the speaker cable on the bottom and the - lead on the top then jumpers. I find the bottom end on my 7B’s to be outstanding. The configuration of the jumpers make a noticeable improvement along with the Sound Anchor bases really make a difference. How far off the back wall are your 7B’s?
So, if you have $4,500 to spend on your system, are your 7B’s really the weakest link? I struggle with the idea of changing out my 7B’s except to maybe the 7C’s but I’ve never heard a pair, but my bet is they’re great.