Hello, I have got an Dell XPS 400 with 3 GB or RAM, and A Pentium D Processor 2.80GHz and an nVidia GeForce 7900GS. I'm upgrading in December to an XFX ATI Radeon HD4670 graphics card and i'm looking at a few Power Supplies. Can anyone help me choose a power supply that wont break the bank and is at least 500W that will fit my case? Thank you very much.
Try the radeon card first in your case. I'm almost positive you do not need another psu for it. You'll know when you need a new PSU if your computer crashes but I very highly doubt it since the 4670 sips power.
There's no need for a new power supply when you upgrade to the Radeon HD 4670. The Dell XPS 400's 375 Watt power supply that provides up to 30 Amps on its combined +12 Volt rails is more than capable of meeting your needs.
Seeing as it is a 7900 gs and it is a pentium D then it has seen quite a bit of service life. I recommend good quality and good price PSU units to replace OEM ones after a year or two to keep avoid any issues. Although Dell PSU's are quite good actually, aftermarket ones are better.
You can accurately determine exactly what power your PC requires for it's current of future config and determine if your current or potential future PSU is sufficient and reliable for the application by using the link below. No guessing is required, just accurate, objective electrical watts and 12v rail amps. to help you make an informed decision.