Where to go from XP-15? XP-17? XP-25?

I've been happy with the XP-15 for a number of years - first supporting my modded AR ES-1, then a VPI Classic 3, and now my Avenger (my final stop, I hope). I love the fine adjustability of MC loading and the gain which will support running carts down to about .2 mV. But with the Avenger I think I've reached a point where I should consider a move, in part because everything I find about the XP-25 seems to indicate it is far and away an improvement over the XP-15. With the inclusion of the XP-17, however, I'm now a little hesitant.

I run two arms on the Avenger, so it might suggest going to the XP-25 is an easy decision, plus the well regarded sound quality (I've heard the 25 a number of times, but not in my own system). OTOH the XP-17 is based on some of the same technology that's in the XP-25, plus it's a one box solution (I kind of like that). The questions out there for anyone who can help - has anyone been able to compare the XP-17 to the XP-25? How do they sound compared to each other? Would the XP-17 be considered a step up or at least equal to the XP-25? If the XP-17 is generally considered a must try next to the 25, I can always run it face into the rack and keep the back end exposed for tonearm and loading changes (not pretty, but effective).

I'm also a little concerned about any change in sound from the previous generation Pass gear to the new (12, 22, 17, 27). I've read, for example, multiple views back and forth between the .5 and .8 series amps, a few saying Pass' reduction in negative feedback and modification to the second harmonic character in the .8 are not to their liking. I hadn't heard if there's been such a (perceived) change in the small signal Pass devices.