Well here's my 2 cents on the whole MIDI Sound Module thing. Be very wary of the Roland... I HAVE owned several Roland products and now I own NONE. Roland seems to really price their stuff high. EXAMPLE: The newest top end Roland V-Kit is well over 5000, where as the Yamaha Equivalent (DTXtreme IIS) costs over $2400 LESS MONEY. Is the Roland better, HELL NO! My Yamaha DTXtreme IIS sounds fantastic, it can do sampling, doesn't have 60 or 70 useless "drum kits" and is very reliable. You can get the Module only for the DTX (DTXT2SU) for around $900 (half the price of a Roland TD-20) and the thing is absolutely amazing.
Another issue I have with Roland besides pricing is where they decide to cheap out to save a few cents here and there. For example, the power adapter for the V kit is a flimsy piece of crap, a very expensive piece of crap, but not pro grade stuff. I have owned a V-kit and a HandSonic , sure they are fun to bang on, but I don't feel that they hold up well under the rigors of live performance (I was setting up and tearing down 6 nights a week) after just a few months they started to show the road wear.
My V-Kit Had a blow out one night and I waited two and a half months for a 45 cent part to come from Roland. They also tried to back out and say it wasn't covered by warranty, but I complained enough to enough people that they only ended up charging me around $150 instead of $450 - All for a piece that was defective, according to the Roland licensed repair guy who worked on it.
In short be very aware of what you are buying, and remember just cause it costs more doesn't mean its better. I know a few guys who have had some of the cheaper Roland kits, and they really didn't like the scaled down features included (small memory, pcm samples of real v drums, etc.)
So that's what I think,
If anyone cares...