I've found that the 2000(classic) has a DISTINCTLY warmer/darker sound than the source. I often sample into it via SPDIF, and even that colors the sound in a fairly obvious way. When used in the manner we all often do: analog inputs driven to JUST before outright clipping, there is often something similar to what I call the "transformer sound". Like the 100-250Hz range has some "hair"...but only a touch. Sampling hi-hats and snares in this way can be dangerous, as they flatten out and lose all sense of depth and space...but for kicks its always incredible.
I've taken to keeping an old DBX 160X(not the newer peakstopPLUS) strapped across the analog inputs and I often just tap the Peak Stop on the way in to allow more of my sample to hit that "golden zone" of great tone without outright distortion. Another neat trick to bring my old MPC 2000(classic) into the modern age is having placed most of my drum library onto a 16GB solid state SCSI drive... This means I had room to use my Maschine library on my MPC! Speaking of Maschine, it makes a KILLER effects/time stretch unit for the MPC... I often create a loop on the MPC, sample it via SPDIF into Maschine, (sometimes chop it up) effects, etc, and then run the whole loop back to the MPC...analog or digital, depending on what I need. It takes longer to write about it on my iPhone than to actual do it in my studio!