The KAV seems to have plenty of power but some dialog can sound "hollow" and slightly tipped up. Also, there is some occasional HF distortion during musical passages on shows (not using it for 2 channel listening).
This reeks a bit of a degraded/faulty amp.
- Sell this "recapped"/used amp (that someone passed off to you, he must be breathing easy now) and cut your losses before it becomes more of a headache.
- Run the 4 surround channels off your Marantz.
- Get 3 Schiit Tyr monoblocks for your front stage (front main/center/right main). It should hit your rig with a rich dose of adrenalin and get you up to speed.
P.S. if you are a loyal Krell fan/insist on hanging on to it... move additional channels back to the Marantz and run only the 2 fronts with the Krell. See if it improves the sound, no hollow bass, distortion went away, etc.