Is my power jinxed?

I run my 250 watt switching amp with a PS Audio Duet on a dedicated 20 amp line. The Duet has been kicking in and out lately, not so much late at night. I tried another Duet and a Quintet with the same results. There is no problem running the amp straight from the wall. I tried the Duet in a secondary system with the same results. My front end runs with a Premier on another dedicated 20 amp line with no problems. I have a whole house surge protector at the main panel. I had a smaller 125 watt amp until July, but the problem just started in the last six weeks or so.
SMPS interaction (somehow?) with the Duet/Quintet?
Same speakers? it was ok with the other amp?
Are you playing your system lots louder now than with the previous amp?
No other house wiring mods?
Speakers were replaced about the same time as the amp. Similar load to old ones. No problems with other amp, no other house wiring mods. System played at same listening level as old amp/speakers as read by db meter. Duet kicks out at lower listening levels too.