I'd like to buy a sound module to keep as a backup whenever my Mac isn't available to use BFD2. I'm looking for convenient, and will go beyond cheap if it's worth it. I'd at least like to get as close to the feel of BFD's 128 layers as possible, and can sacrifice the number and variety of patches: I don't need to be picky about the sound as long as it sounds generally like a drum kit. I don't really know this kind of gear, but I suspect if I want BFD-like playing response, I have to pay more, and the unneeded extra sounds and functions will be included in the higher price. But I do really want a small footprint: if I have to go 19" rackmount form factor just to stay in the ballpark of what I want, I won't bother because then I might as well use my keyboard/workstation's drum sounds.