Yamaha DTXpress/DTXplorer/DTXtreme

I'm looking to add to the basic old DTXpress setup, and purchase an 
extra pad & lead. I'd just like some opinions on whether to stick 
with a Yammy pad, stereo, cymbal or whatever, or whether there are 
better, cheaper, 100% compatible options.
As ever, your help is gratefully appreciated,

Cheers,

Welsh Thunder.