Yamaha DTXpress/DTXplorer/DTXtreme

Hi Guys.
I have been playing with the idea of buying a DTXPRESS for about 12 
months now and right now i am just about on the verge of wanting to 
finally do the deal. But I'm anxious and have some questions. 

Firstly I want to find out where the cheapest place to buy from is. I 
live in London and so any online store in Europe would be good. 

What can I expect to pay for everything I need to get started?? 

Is this a good kit to learn on? I have limited playing experience on 
a kit I bought about 8 years ago but only used for about 12 months.

I am eager to utilse my laptop with the kit should I decide to 
purchase the dtxpress. What is the available range of external sound 
cards for laptop computers like. What price can I expect to pay for 
an entry level one??

I think thats about it for now.
Any help appreciated,
Brian