“Didn't even know there were any good ones for under $15k”?
Ummmmmm! Yes, there are a few. Example, Cary Audio SLP-05 with the Ultimate Upgrade.
check out the article on Stereophile. You don’t have to pay $20–80K to be the best sounding
https://www.stereophile.com/tubepreamps/906cary/index.html