I tried something today that I really like so far and thought I would share. I have a powered head but have been using a pair of Yamaha DXR10 powered monitors off of the monitor output because I prefer this instead of a guitar cab connected to the power amp.
Just for grins today I also connected the output of the KPA power amp to a 4x12 guitar cabinet (Soldano 4x12 with Celestion G12H30 speakers). My DXRs are doing more of the work than the guitar cab but the guitar cab can definitely be heard and seems to add a bit of that elusive "amp in the room" that everyone strives for. I get a fuller tone with better bottom end and a bit of actual guitar speaker coloration in the mix.
I left the cab output on since the DXRs need that but honestly when running a guitar cabinet alone off of the power amp I can't really hear much difference between the cab on or the cab off and both sound fine to me. I tried this setup using a Boogie 1x12 Thiele cabinet with a Mesa MC30 speaker but I didn't like it as much as the Soldano 4x12 but I don't really like that Boogie cabinet for anything. Bought it to match my JP2C head that I traded for my KPA. That's about all it was good for. Aesthetics. My girlfriend tells me that it is very important for things to match.
This is just another alternative and I like the way it sounds and figured someone else might benefit from it. If you have a powered KPA try it.