Krell Evo 600 issues/replacement advice

I thought I’d just made the final major upgrade to my system with addition of a D’Agostino Momentum preamp —stunning component with flawless performance.  It is connected to a pair of Evo 600s, and I was really satisfied.  They are powering Revel Salon 1s.

this morning one of the amps kept tripping it self off after the red light on the front glowed for around 5 seconds.  I checked all the connections and tried again.  This time the red light stayed lit, so I pushed the power button on the front.  The light turned to flashing blue (as it the norm) then the light went completely dark.  I played some music, and the amp is functioning without issue, other than the light ring around the power button being dark.
I sent off an email to Krell to get some assistance/arrange to send them in for service and discovered their factory is closed with no prognosis for opening.  So, I could be living on borrowed time...

I’ve had the amps for 10 years and really like them, but their power consumption while off/standby  (red light around the power button lit) is pretty high.  If I’m away from home for a day or two I usually turn them of from the back.  That’s a minor inconvenience, but still an inconvenience.

I’ve had several dealers tell me their performance is still in the upper ecelons, but there are better options available, so I guess my upgrade journey might not be complete after all.  MBL Noble, Gryphon and Krell Solo 575 XD were mentioned as replacement candidates.

There are a couple sets of Momentum 300 mono amps advertised here and on US Audiomart, but a dealer told me that I should get Momentum 400s instead.

Has anybody had the opportunity to compare the Momentum 300s and  400s, or have any recommendations on other mono amps to,consider if I have to replace the Evo 600s?

Thanks

 Mitch