I've found Sound Forge, ReCycle and the MPC Editor to be the most efficient way to record, chop and program samples for use with the MPC.
Record, trim and process your samples in SF, save em' as a wav file. Chop it up in ReCycle and export the slices. Use the MPC Editor to drag and drop your samples into a program and save the program and sounds to zip. Load it up into the MPC and off you go.
You can do all the chopping with just SF but I find using all three of these programs really streamlines the process.
Reason doesn't allow you to record or edit audio, not in the way SF does anyway. You can tweak and process audio but you cant chop or trim within Reason. It is essentially just a sample player as opposed to a sampler. Don't get me wrong Reason is a great production tool but for what you want to do I'd say Reason is not the answer.
You might want to check out the new version of Cool Edit(I forgot what it's called now) it's a very good audio editor and doesn't cost nearly as much as SF, it didn't used to anyway, they might have raised the price.
