Steve,
for the exact reason you describe, I see the rubber pads regardless. As you also said, we have unlimited sounds at our disposal. So if tapping on my desktop can produce a full array of drum sounds except it is a rubber pad, so much the better. There is no way I want to spend over $750. The reason I said $750, was the Yamaha 450 at about $675. I did not think about a used set but I will look over at a few sites and see what I might find. This is not a primary function for me so something that will produce a few of my own rhythms will be great.
So my guess is with all of the pads you use, you are able to use different sound modules and just keep connecting them? Additionally, they all show up in just ONE midi track?