For true Phil Bombs, consider a (or, better, two) JL Audio F112 (or two F110s). Beyond that, and recognizing that you enjoy the surround/multi channel experience, if you are really looking to capture the live Dead sound, you should still consider going 2-channel. Peter S (and others) makes good suggestions about electronics. Re speakers, given your room size and configuration, consider switching to floorstanders with more cabinet heft and lots of mid-range clarity, extension and power handling -- so essential for Jerry's guitar work. I really question whether you're current multi-set up comes close (it may well; but I fear you are missing the core; and you must too, hence this thread). Or, get monitors with those qualities and add two subs. The advice about room treatment is spot on; it makes a huge differenence, and can be accomplished with WAF.