Hey Mojo, it seems your 600 would be perfect except for the tightness of the 400 and "chest thump" and "slam" (according to 2 reviewers) of the JL 113 & the Ultra-13. Do you think a 2nd 600 would help with those 2 issues? (Pie in the sky question, of course)

I have a single 500 and also feel as you do about the "chest thump" question.

Epic 80 / SVS PB13 Ultra
Denon 3805 / M2200 Outlaw Monos /
Sammy 55" LED