Currently, I am using newly built Cornwalls (sorry, it's been only a few days, can't resist bragging, LOL) with my GU50 SET (GU50 wired as triode, fixed bias, custom wound iron). The sound is amazing... Always been a big fan of SETs: I like coloration of the sound by single-ended amps, and with Cornwalls the notion of "plenty headroom" becomes evident through clear, snappy bass at low(er) volume, and for the lack of better word, "full bodied" sound at higher volumes...