Some random observations,
1) your choice of amplifier, especially if you are considering a class D amp, will be very speaker dependent. In my case, I was driving a pair of Opera Platea's with a Prima Luna Prologue 5 (primary system) and tried a Class D Audio CDA 250 and thought they paired very well. The Class D sounded like schiit though with every other speaker that I had in other systems.
2) I am curious how much heat your KT 88's (do you run 4 or 8 of them, btw) could be throwing out. I have never felt this way with my PL5. Granted it is not a near field or desktop set-up.
3) Hard to replicate the PL/ tube sound if you are happy with it without using tubes. I have in use and/ or have used the Outlaw RR2150, Rega Brio, & Musical Fidelity M3 amplifiers and they were not as satisfying. I am using a Rogue Sphinx now in a secondary system (Golden Ear BRX speakers) and it is pretty good, but I enjoy my PL5 more (Zu Audio Dirty Weekenders speakers).
I would stay with my PL gear. If I were to try a different tube amp, I would consider Raven audio.
Rich