what can the 2500 do that the 1000 cant

why would someone want to buy the 2500?

Oh boy. You may have unwittingly prompted another Antonym vs. Jahrome 3 page slanging match with a question like that.

Anyway, the differences are mostly physical these days:

1000: smaller pads, 6 outputs, 2x MIDI in, 2x MIDI out, you can add a hard disk, extra RAM
2500: larger pads, 10 outputs, 2x MIDI in, 4x MIDI out, you can add a hard disk, extra RAM and a CD RW drive.

In terms of what you can do with the machines, using the standard Akai OS, the 2500 is more flexible than the 1000. If you use the unofficial 'JJ' OS (see the other 1K forum dedicated to that OS), then the 1000 has more features than the 2500. However, JJ has turned his attention to the 2500, so there will likely be a more capable OS for the 2500 out soonish.

Take a browse around the MPC Comparison forum, there are lots of threads that discuss this topic right there.

thanks man. i love the 1000 so much that i was thinking of possibly getting a 2500 as well,but i dont really think its a must.instead i will learn the 1000 in and out.
thanks again

yea u should do that , good idea .... then u can upgrade if ur still married to your 1k haha