You already have the MPC 2000. you could get a cheaper keyboard. Just get one that's expandable so you can add sounds later.
With the k2000 you can sample like Chris said but you don't need the sampling option to do sampling with it. You can buy extra SIMMS and then load the samples with a SCSI zip drive. The sampling option alone costs around $600. You would need extra memory even with the sampling option installed. A friend of mine has used the k2000 for hip-hop
and has made a (very) good living using it. He advised to get it, and I did but let me tell you that it's a b@$tch to learn. I'll get there.