If your looking for bang for buck, try this combination:
Tannoy Reveal Passive Monitors (UK£176)
Servo-170 amp (UK£150)
Behringer MX2004a (UK£195)
The Behringer has 8 mono channels, 4 stereo and a couple of stereo aux returns and a line in (on RCAs) - giving 20 input channels total. Should be plenty, even if you upgrade your MPC to the 8 output version oneday. I run my DJ mixer into the Behringer, and using the 'alt send' and PFL buttons can send any signal on the mixer to either my sampler or PC for recording... Its really cheap and flexible... Some people have issues wtih noise at high volumes with behringer stuff, but i've had no problems, we all want a mackie desk but for under £200 you can't go wrong... Just remember to budget for cables - they get pretty steep for decent ones...
If you can't afford all this at once you could always run your MPC's stereo out into a line input on your DJ mixer for now, and the dj mixer to the amp... If you look around for this kit second hand you could save a fair bit too...
If you want more info on how i've set up my mixer-PC-synth-samper-decks routing just post back... Its amazing how flexible the Behringer is, and if you run out of channels (all 20!) you can just buy another for £200 and 'daisychain' 'em - a 40 channel board for under £400! Plus you get decent EQs on the 8 mono (3 band swept) and four stereo (4 band) channels. Plus you get 8 mic inputs/preamps on the mono channels to give you future recording options.
Anyway thats what i've got and i'm happy with it all...