Yamaha DTXpress/DTXplorer/DTXtreme

Hi, just wondering if some of these multi-pad units such as a Roland 
SPD-6 Percussion Pad, ROLAND OCTAPAD Pad-8,  Roland SPD-20 
Percussion Pad will work with a DTXpress module or even an Alesis DM 
Pro module?

I see that some of these have their own internal sounds too, don't 
know how good though!

Any OTHER multi-Pad idea's models, makes, where I can see one, read 
about it that are just simply multi-pad units with no sounds that 
can be connected to a drum module?

Thanks, Steve