Yamaha DTXpress/DTXplorer/DTXtreme

Hi all, just joined because I'm ready to buy a DTExpress except I 
believe it's the Dtexpress2. Maybee i can get some info on the 
difference between the two. Also what is the difference if any 
between Dt and Rolands compatible model if any difference. I'm an 
acoustic Drummer but if a don't get an electronic kit I'm gonna get 
thrown out :-) I'm sure
you guys know what I mean. I hope their quiet :-) Also can I hook up 
any more pads to it for a slightly larger kit.
Any info at all will be greatly appreciated and hopefully i can 
return the favor when I get familiar with them.