I am in the same position as yourself, although my bass is a lakland 5501....same pickups and preamp as the cort. After doing some research, it would appear that the preamp is more of a weak link. One guy installed the mk5's along with the usa bart preamp and ended up putting the cheapo mk1 pickups back in(along with the usa preamp!!)...the mk1's are i think split/reverse P style so with that in mind, fed with a decent pre, could sound good.
I myself are looking towards the john east uni-pre 5....i may change pickups at a later date...we will see!
Anyway, good luck with the mods and let us all know what you think when done.