I've not looked at all the PCs you have lnked to, but they do seem to be on the right lines - Core i7 and minimum HD5870 graphics.
I'm sure myself and a lot of other peolpe will take a more detailed look at this later, but for now:
1. If you are not comfortable with the reputation of a company then don't use them.
2. Make sure you are getting a very good PSU in your new PC
3. Do you need a new monitor and operatring system. If so, Win 7 is the only sensible way forward. What size monitor would you be looking at? A good display makes a world of difference.