Need advise on preamp.

I have issue with the current preamp, Classe Audio SIGMA SSP is what I'm currently running to send the signal to bi-amped system consisting of 2 Thresholds S500 series one with optical bias powering  JBL 4367's.
As sigma is a excellent device somehow it does not perform same for every thing I'm trying to play.
It does great job playing classical, progressive or electronic how ever once you start playing something more aggressive like heavy metal sound turns in to mud, non separative mas of sound. I'm looking in to analog preamp like Threshold  FET10, that I own how ever I can't use in bi-amped config since FET10 does not provide double output.
So what would you guys recommend that would be FAT10 or at minimum Nakamichi CA5 performance and it has provision for dual output it. has remote control and is black finish. Any idea will be greatly appreciated. I have flexible budget but if possible I like to stay in the range of 5k at less there is big gap in performance to price ratio than I'll consider budget upgrade.

Thanks