Best graphics card that works with 375 watts?

[Atomic Rooster]

Nope, at the time those were released, 450W was plenty for most high end systems.

 

[worshipme]

Dell aren't going to spend more money than they need to on their systems. If when they sell it, it only requires a 350W PSU, why spend more?

As for the GPU, I'd agree with AC, the 9800GT. HD 4670 if you're worried the 9800GT won't run.