Why does my system now have shrill top end.

Did you damage your speakers? Playing too loud or clipping?

Not sure it would be room acoustics as there is no improvement as I walk around the room. The amp is plugged in directly to the wall and thus it is possible that ac noise is the cause but the issue is so pronounced and the P5 (only front end components plugged in) indicates a pretty decent sine wave and voltage that I tend to think not.

I would hate to think it is related to the Pass Amp as at 88 pounds it would not be fun to send back to dealer. 

Anything is possible but both would have to been damaged the same way and I don't play the music that loud. And, as I don't have any equivalent quality speakers to substitute I have no idea how to test this.

Consider putting noise filters on all the new equipment and lines in the new kitchen.

As well, the person who did the electrical system for the kitchen, may have altered your room’s connectivity to get the kitchen on line.

Consult with them.

those are probably the major potential culprits.

I’m guessing one of the new pieces of equipment in the given kitchen has a very dirty ’pulse power supply’ and is injecting noise into the AC which is impacting your sound space, electrically.

This can be quickly tested via shutting down the new kitchen at the AC power panel, then adding kitchen breakers back in, one by one, listening the whole while. If this is the case, the culprit outlet and associated kitchen gear will show itself. Lighting is also on this list. Especially CCFL’s and LED bulbs.

Best cheap tweak ever for audio shows:

BRING INCANDESCENT BULBS to the show and put them in the bulb sockets of the room, and turn them on.

the filaments of incandescent bulbs will knock down (partially absorb) the noise peaks of the dirty ac power on the given lines in the given hotel room.

If it's not the system, the room or environmental factors, then all that's left is you.  What's different about you since this has occurred?  Change in medications, different diet, exposure to loud noises, etc.?

But before worrying about that, I would disconnect and reconnect every system interconnect/cable.