I have just ordered a kp3, havent recieved it yet, but have been rubbing my hands together with glee about how its going to integrate with my mp, and my setup ingeneral. and reading the manual pretty heavily. avauialabl here
http://www.korg.co.uk/downloads/kp3/sup ... M_EFG1.pdfre, the sample capabilities, From the kp3 manual p. 19:
it supports up to 2gb sd cards, each of which can hold up to 99 .wav or .aif files (whose file name must be a two digit number followed by the file extension) and 99 of something the manual just calls "sample data" - its either .snd (but i expect then they'd just say so), or perhaps a dedicated file type; could this be .kp3

aaaaaaanway, the card also holds some info about fx and midi program setup and stuff.
As to how much samples it can holding while youre playing. from what i gather 4 at a time is the max (one per pad), although you always haves the option to resample, so you could live resample 3 samples onto one pad, then you'd have more space for other ones.
I imagine you have to load up each 4 samples as you go, which would be a headache in a live set scenarion, but by all accounts the kp3 is a killer maschine in combonation witht he mpc1k.
peace and happy cookin
al