Turns out the Corsair HX1000 is dead, bad PSU jumper probably killed it right off the bat upon initial bootup attempt over a week ago. I found this out today when I got around to switching the Lepa back in and getting a different secondary PSU jumper (got an Add2PSU unit this time). I had the Corsair hooked up to the 2nd & 3rd 980Ti's, booted up, got into Windows and couldn't figure out why they weren't showing up in Windows. After all, this time the system had no issue booting, the cards lit up, seemed to be going fine (seems they get enough power from the pci-e to light up and show up in BIOS, but not to be considered functional). Didn't take long to figure out what was up, I pulled the Corsair and did the paperclip test---FAIL. It just doesn't end. lol
I guess I'll get around to ordering something to replace it, probably not necessary at this point with the Lepa back in there but that was the whole point of getting the pedestal with the psu cutout. Maybe one of those Seasonic SnowSilent models, they would look nice in there, shift the Lepa down to full GPU only duty. Certainly could get by no sweat on the 750W version if it wasn't powering any GPUs.
On the positive side I did get around to completely purging the loop of air today, I'd been living with it gurgling since initial fill. Nice to have the silence back.