Old thread I know but let me share some wisdom that has made me love my Kemper for bass.
You want to use the parallel path feature and you want to cut high frequencies to taste and you want the mids and high end running through a guitar amp profile or something higher gain. I usually high pass the at at around 180hz or even higher, until it sounds correct. I use an external compressor, Empress one and just get it to level out the signals and then I use a little compression to hold the two sounds together at the mixer.
The biggest problem most people have is they dont attack the bass correctly. You have to have a really clean, hard attack, pick or fingers. Its not a pluck its a hit, through the strings. Fresh strings and you got it