@jimbones I had the EH KT88s in my Cary SLI-80 stock, and never could get myself to warm up to those - at all. Kinda lean and non-engaging in that amp. Did not like then much at all for my amp at the time. Depends on the amp too, and how they are driven, biased, and of course how they work with the rest of your system of course. Your friend can probably tell you why they are available as loaners.
I only kept them to give away with the amps as backup test tubes. When I upgraded the SLI-80 internally, the next tubes I tried was reissue new Genelex Gold Lyon KT88s. They were nice tubes (balanced top to bottom) for the quad price $ at the time. My buddy did the PSVane KT88 MKIIs, and those had a little more body and warmth, slightly rolled off on top taking the etch off, and he's been running them 2yrs, loves. them, they did well in his amp.
As for the overly pricey and limited availability EAT KT88s, maybe I spoke too soon, I noticed just now on a few sites they are unavailable, out of stock. When I mentioned birthdays, christmas time, or bucket list buy - here is why. You could call TD and ask them about EATs, and they do sell other decent KT88s too. Hold your breath now, LOL, seems they may not be available much right now anyhow...ugh. https://www.tubedepot.com/products/eat-kt88-diamond-power-vacuum-tube-matched-quad?srsltid=AfmBOoqggHuzJXgBXwvysqp1ORO7lRJ0AXCrUvY4B9PwrTacqQ-pyN2B
. I’ve never tried them but I might if my amps could run KT88s like yours can!