do i need an mpc??

For what you're talking about doing, go with the SP's. Since your just playing your sounds live, and don't necessarily need the higher end sequncer of an MPC, the SP's will work better, they don't use RAM and can load huge sound files and stream directly off of a Compact Flash card, so technically with those you would'nt even need to chop up your song, you can play the whole mix off of a Compact Flash.

How bout Akai S6000/5000 with usb expansion or Z4/Z8 sampler since it integrates with computer real nicely using aK.sys.

I'm not sure if you need a sequencer but those MPD joints can be powered using power supply not included

Hook that up to the rack sampler with midi and you can trigger the samples via midi controller of choice.

If you need a sequencer, I'd look at older MPC series MPC2000/2000xl. They're real cheap nowdays, I seen MPC2000 in $300-400 range on craigslist.

Now you have a rock solid sequencer/midi controller paired up with one of the rack samplers above one hell of a setup.

jbone...i think you hit the nail on the head there.
until today i was 100% sure i would get the mpc500 but the roland sp555 now looks like the beter way to go.
just spoke to a thomann.de head there and he set me straight on the whole scenario.

thanks for the replies lads...really appreciated it as this feels like the most important decision i've ever made

see ye on the dark side