which is a better match for best results

Had both and admire both, but I would say for the best overall performance go Krell.  The AR can give a bit fuller, rounded sound but slightly hazes leading edges is less incisive.  Have also had gain compatibility issues when matching. ARC preamps with solid state.

auxinput speaketh truth!

Ok, not sure what absolutist bible exists that portends the efficacy of all amps for all music types!  THAT is lunacy.  Classical, jazz and rock can favor very different frequencies and musical tastes.  What can make strings and woodwinds sound natural can make cymbals and upper register piano sound dull and rolled off.  Amps and systems in general have different voicings that can either accentuate certain frequencies or not...of course neutrality is the goal (for some), but can be elusive.  Cables are a whole other realm, as well as source material and playback equipment.  It’s called design...hello!!  Not all amps, or anything for that matter, are made exactly the same.  Are you “All amps sound the same” people drinking the Audioholics protein fueled punch?  Perhaps you were speaking to the ideal amp which would not favor any particular music?  In that case, carry on.