Technically you could just load the MPC samples into logic and sequence there... either keep the mpc as a glorified drum pad or get, say, a korg padkontrol (mine is still kicking after about 4-5 years, great value considering) or the AKAI midi pad, I forget what it's called, but probably has a more similar action / look to what you're used to.
Another option would be to spring for something a little more multi-channel - ensembles can be had for $1200 - $1500 on eBay, or there are several other options. If you got an interface with digital I/O, you could use the MPC that way - it has digital outs, right?
Any way you cut it, though, you're going to want midi. Others have suggested the cheapo USB cords, and those are fine, actually, but you could either get midi with your interface or look at something like the M-Audio Midisport series - options from 1x1 to 4x4 I think (1 to 4 midi ports, 16 channels each, leaves a lot of room for your expansion or use with multiple synths simultaneously - depends on your needs).
PS: I get that the MPC is a staple in some types of music - that's cool, but it's arguably redundant with a computer. Keep it for the vibe or the workflow if you want... no judgements either way.