Here is an update from about a year ago, its a long story.
I purchased a Lexicon MV-5 as an substitute while my Krell was sent to the Krell headquarter for repair. My audio technician and installer sent a detailed mail to Krell outlining every issue with the Foundation. Krell called back and said they felt the 4K was performing properly. There was no addressing the list of issues provided to them. The unit was reset to factory standards and returned and set up in the system. It performed as it did before it was sent to the Krell headquarters. In other words, the base/subs play sometimes, not all the time. Most of my music is streamed from an iPad to Apple TV. While listening, and without warning, the subs will start playing, like the volume for the sub was turned from 0-10 blasting you out of the room. The subs will play for 3-5 seconds then stop. Other times, they will play for the entire song.
In the meantime, I tried an Arcam AV40. The tech/installer and I auditioned a few songs and videos, then went back to the Krell. The Arcam video and sound were disappointing and underwhelming compares to the Krell. I just wish that I could get the Krell to perform properly, when it does, it's exceptional. The subs are top of the line B & W.