I believe the ASR does the keygroup thing. Most rack samplers do also.
Software-wise, most samplers are keygroup-based (apart from BATTERY maybe)
What do you wnat to do exactly? if you are abig pianist and wantt load complex multisampled pianos etc, then look at the MPC4000 or MV8000 - or a keyboard workstation (triton, motif, asr-10, etc)
If you are not a big pianist and want to simply have access to a a bunch of notes from 1 sample quickly, you can use the MPC1000's "16 LEVELS" mode. Basically it turns the 16 pads into 16 notes of a same sample. It gets the job done in many cases, although it is not the same thing as keygroup.