Also, are you planning on using the 400W PSU or do you have a new one in mind for new build.
This build I estimated some things is at 271W (it would be good to check): eXtreme Power Supply Calculator
If your PSU is also 8 years old, I would replace it :|
Changing to a Quad puts it to 316W
and putting in a newer video card:
radeon HD5770 bumps it to 330W
radeon HD 5970 eats it at 495W