Planning to overclock the PC?
I would suggest G. Skill HZ PC6400 or Ballistix PC5300 if you are planning too, they both easily get 1000MHz overclocks.
The P5N32 sli boards tend to have a lot of problems with ram compatibility and I wouldn't suggest one.
The P35C_DS3R is a very good board, the new chipset meaning it supports the new Intel 45nm processors that are out next year I beleive.
The soprano is a very cheap plasticy case. Take a look at one of the LianLi's or a Akasa.
650W PSU is a overkill for your PC. Would recommend a Corsair 520W, they are very quiet and super reliable.