I bought a new PrimaLuna Prologue Four from the 'deals' section on Upscale Audio, just a couple weeks ago. I bought to match with my new Zu Omen Def. Mine was open box, paid $1,200. Screaming deal.
Anyhoots, since then, I've inserted KT120, for curiosity. I emailed PL who told me to adjust the autobias screw on the circuit board. No need to do that unless 120s are inserted. Fortunately I own a digital multimeter, the explanations are within the 'tube rolling' section on the PL website. I'm also rolling the little tubes, again out of curiosity. Everything is breaking in, including new Zu cables, so I'm just enjoying the sound in the meanwhile. May post update in a month or two. Actually of course now I'm thinking of PL monoblocks, like lots of us PL owners.
8 years ago I owned a PL integrated, wish I had kept it. I bet it's still going strong for someone.
Long story short: PLs are amazing products! You cannot go wrong!