Upgrading my graphics card?

[Your Computer]

Yes, that was actually the only upgrade I was going to do. I don't really think I will have to upgrade anything else.

In that case, you won't need more than 550 watts. I'd recommend a modular PSU, as i don't expect you to do as great of a job as Dell may have done with the cable management. Brand names i recommend include Corsair, XFX and Thermaltake, but go by reviews anyway. I'd also recommend trying to get a PSU that is at least 80 Plus BRONZE. If you can't find a 550 watt PSU, then go for 600, but don't go overboard (e.g. 800) if you can't find that either. Keep in mind that any power not used from the PSU gets converted into heat. The Dell case you have is designed where the PSU pulls in air from inside the case (which is bound to be warm already) and not cool air from outside the case. The temperatures from the new graphics card, especially since we're talking about NVIDIA, will increase the temperature inside the case. You wouldn't want 300 or more watts being converted into heat.