Have you tried bridging your current amps as opposed to running them bi-amped? I'm not sure if it will be better or worse but given they are rated 4 ohm stable while bridged it is worth a shot. 500 watts 8 ohm and 800 watts at 4 ohm in bridged are some serious numbers. Especially given your speakers are rated at 90db.
For the record I have a JC5 and absolutely love it. It really brought my Revel F208 speakers to life. I upgraded from a low power integrated though so it was a substantial improvement.