Definitely go with KT150s. I went from 88s to 120s and while that was a great improvement, I had some of the artifacts mentioned in previous posts about the 120s (it’s been awhile so I don’t remember exactly what I didn’t 100% love about them, even though they were a good upgrade from the 88s). About 6 months later I had read all the write-ups on 150s, and while 8 of them is an expensive upgrade-gamble, it was totally worth it. Noticeable right off the bat, and with some burn in even better. A much bigger jump than from 88s to 120s. I would always have 150s in a component that could take them (until they make 175s or whatever!).
If you’re PL can take 150s and you don’t mind leaving the cage off (it doesn’t fit any longer), I haven’t read a single post anywhere where someone upgraded and regretted it.
Just for clarity’s sake, I own super efficient Zu Soul Supreme speakers (the combo is killer), so the 150 upgrade for me was NOT about power increase but to get better bass and top end (which they gave me in spades).
Also, if you’re debating HP or not (vs. the "normal" Dialogue Premium), the headphone amp is truly outstanding as mentioned. I have HiFIMan HE1000s and it drives them superbly--probably as well or better than the $4200 McIntosh HP amp I also own (because of the rave reviews with the HE1000s). I love the McIntosh, but it’s not better and I’m probably going to move that whole rig to another system to simplify my main listening rig.
