I bought the unpowered rack version, thinking that I would use my Fryette PS100 for the power section. I thought there might be a way to use the "two channels" on the PS100 and run one for the Kemper and the other as the load box/re-amp. I discovered that it doesn't work that way and these supposed two channels in the PS100 are just variations on the same channel with different EQ'ing. IMHO, using the PS100 exclusively to power the Kemper is a waste of what it's capable of doing, so i started looking for a decent (not too expensive) dedicated tube power amp. I settled on a Carvin T100, and got it added to the rack yesterday.
All I can say is.. WOW! What a difference. So much more "alive" sounding with the power amp vs. the PS100. Not knocking the PS100, mind you, as I don't think that the designers had powering a Kemper in mind when they made it. I don't know if there was some kind of path through the PS100 that affected the overall sound of the Kemper, or if the difference in power tubes made that much of a difference (6550's vs. 5881's) but I'm glad I made the switch.
Honestly, I was about to get rid of the Kemper because it was "cool" and all but it just didn't move me like a real amp did. I don't record, or play out where I could use it direct to FOH, etc.. So, it just seemed like overkill for my needs. I had pretty much made up my mind to move it along but then this whole mess with the tubes came up and I decided to hang on to it thinking it might be handy to have around... You know, just in case. I'm glad I didn't sell it now.