Krell 4K Processor sounds like the guts have been pulled out

Equipment:  Krell Foundation 4K Processor, Mark Levinson Reference Amps, Revel Salon # 2 speakers,  2 B&W ASW 12CM SUBS, great cables, electrical supply, ect.
Problem:  Krell & entire system used to sounds awesome, now the bottom is missing.  There is no punch to the music. The volume must be turned up 50% more to achieve the same listening level.  Low level listening was sweet and full, now it is very shallow focusing on mid and high range music, leaving out the bass and thump.  Subs rarely kick in-all adjustments and settings predicate the subs should be working.
Recent change to system:  New Xfinity cable box-latest generation.
Attempted fixes:  My AV specialist has gone through the system to check all settings, which are spot on.
I do not have a center channel speaker, (I find them annoying),  and I like listening to musical performances at concert levels, in stereo, as they play on TV or play back off my Xfinity DVR.  Does the Krell suck, or has it gone bad?  Last update to the Krell was late 2017.
Hello robertwdavie,

     I should state upfront that I don't own/use a Krell Foundation but I did  need to update my Xfinity box to the latest generation when I recently upgraded to a 4K Bluray player and hdtvy.  I also just read the following review on the 4K Foundation and suggest you may want to do the same.

     In the review, it states "One nice part about buying a Foundation from a top Krell dealer is that the setup task becomes the dealer's problem, and any learning curve for the Krell online interface is also the dealer's concern. If you want to be more hands-on or DIY, you will need to take a little time to learn your way around. "
    It seems like you've received this service from your dealer but are taking the A/V installer's word for it that all settings are correct. The review goes on to state that you first need to make sure you have the latest software update for the Foundation from Krell.  
    The review also states that using the unit's Ares room correction software's setup option for automatic speaker setup and room EQ using the supplied mic, does not yield the best results.  I believe the installer may have used this option in your setup for expediency.
    The reviewer states "You can run the speaker setup and not the EQ if you like, and advanced users have the option to manually adjust the crossover and delays in the Edit section." He determined the audio performance of the Foundation was significantly better with the EQ turned off.
     My suggestion is to either try this yourself or invite your installer back to make these adjustments to your preferences.

Check to see if the cabling to the sub has been misconnected or bad.

Next, try disabling sub in AVP and set side speakers to large, with bass track going to them.  See if this restores your bass.  If so, it means problem between AVP and subwoofer.

Nothing was wrong with it. It just needed to be reset and have firmware and DSP initialization that updated the DSP software. Its sounds awesome now. I love it.