Yamaha DTXpress/DTXplorer/DTXtreme

Hi All

This is my first post.

I have an oppertunity to buy a demo dtxpress 2 for a really good price.
But i was looking originally at buying the 3 series. So I have a few
questions.

1. Is there a huge difference between the two that would warrant the 
          extra cash 
2. will i be able to load drum samples into the xpress 2 module

3. Can i use pc based samples with the dtxpress 2 series.
4. Can you choke the dtxpress 2 cymbals.

I will be using the set to mostly record with Sonar 4 and wavelab.
Can anyone else suggest what else i would need to get the best sound
(i'm still feeling my way around midi sequencing)

Thanks All
Clint