Guitar speakers all really colour the sound. If you want flexibility this is a bad thing but if you want a consistent flavour across all your tones then it can be a good thing. The point is, there are no guitar speakers that “work well with the Kemper”. There are however, guitar speakers that some people love and others hate and no one can agree about it. Long way of saying, whatever guitar speaker you personally like with a regular amp is probably the best guitar speaker for you to use with the Kemper.
If you're looking for a full range speaker to use PROFILEs with the CAB slot activated, than I can just point you towards the KONE speaker - to me it simply sounds the best.
If you are looking for a traditional guitar speaker and want to use it without the CAB portion of a PROFILE, than you might like the relatively uncolored Eminence Cannabis Rex, which is what I used live before the KABINET.
...so in summary you have 3 options of speaker type:
1) Guitar speaker - as mentioned there are no "special" ones, they react differently for different profiles and sounds etc. and massively colour the sound
2) FRFR which are way more transparent but some people find them clinical
3) Kemper Kone ( which you requested non Kemper but not sure why you ruled it out) which to my mind is best of both worlds.
The Eminence EM12 is working great for me as an alternative. I do use it with the Kone function engaged in the Monitor Output menu and some slight tweaking to the Monitor eq, I do not use the imprints though. It's not an "FRFR" solution, but it does have a more neutral response than a lot of other traditional guitar speakers, and it is rated at 200 watts.
