Harry's right on.
I've got the SPD-S and it sounds like what you want.
The new SPD-30 or other modules with internal sounds (Alesis DM10, Roland TD-xx brains, etc.) are also an option but if you don't care for the internal sounds, you are stuck.
You can work on sounds in any situation and transport them over to SPD-S via Compact Flash card. You can also sample on the fly. That means you can just hook up a mike and record right then and there where you are. You can also hook up an MP3 player or CD player directly and pull sounds from that.
The above features are why the SPD-S still sells and is pervasive n the electronics world after being out for a few years without any significant hardware upgrades.
Jim