Yamaha DTXpress/DTXplorer/DTXtreme

I was wondering what the differnces are between the I and II modules.
Does it have better cymbal sounds... or does any one have a good 
custom cymbal sound in the dtx1 that really has a bright sound that 
projects well. It seems at times mine are not loud enough when 
playing. Would it be worth the money to upgrade to the II if I was to 
find the right price for a used one?

Also I have the DTXPRESS I module a pads. But I am wanting to upgrade 
to a larger mesh head pad for the snare. Any sugestions?  pintech?
hart?  build my own?