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.

I heard the Krell Evo 402e with a Phantom preamp, which is the newer version of 202.  It was an excellent result for both jazz and rock.  Of course, your choice of interconnect and speaker wire can always influence things.  Keep away from silver, lol.

auxinput speaketh truth!

which is the best suited pre amp for rock and jazz

Electronics can in no way favor a certain form of music! Can't happen- no how no way.

@atmasphere - well, I beg to differ.  There will be some systems out there that are too bright or with too much silver.  They may be okay for things like jazz (piano trio or quartet), but with rock music, they just get to bright/harsh/thin.