Windows 7 - Help on Power supply

I apologize in advance since I am not very technical and first post.

I have a Dell Inspiron 531
Processor: AMD ATHLON 64 X2 Dual Core 5600+ 2.81 GHz
RAM 3 GB

Running 32 bit Windows 7.

I had the standard NVIDIA card that came with the computer. I have a 19 inch Dell monitor (VGA connection).

I obtained an Apple Cinema Display 30'' for work (DVI connection). Since I needed to run both screens with nice image quality I have to upgrade my video card.

I was thinking of RADEON HD 5750. My current power supply is 300W so I know that I have to upgrade this. I need help in determing what is a good power supply unit. My buget is under $100. I have a PCI E slot on my motherboard so that is not the issue.

I was thinking of
Antec EarthWatts EA650 650W Continuous Power ATX12V Ver.2.2 / EPS12V version 2.91 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC "compatible with Core i7/Core i5" Power Supply

But some people say Antec is suspect and on the AMD website it does not list this as compatible with the 5750 (though I think it should work).

Any comments would be very helpful. If you think I should get another card rather than 5750 also advise.

Thanks in advance.

Go here:

eXtreme Outer Vision - eXtreme tools for computer enthusiasts

It's a reasonable calculator for how many watts your stuff uses.

I estimated based on what you said and it said about 240 watts used at 90% load. It recommended a 288 watt supply.

You may think that is ridiculously low, considering everybody says any self-respecting man needs a jillion watts.

So add a couple of hundred watts because the calculator is surely wrong.

Say 500.

Get a 500 from a good brand: Seasonic, maybe Corsair; probably modular. No problem under $100.

I just built a very powerful system that uses 80 at idle and 160 at full load by actual measurement. Look at my specs. I have no video card. If I had a high powered card, I'd probably go 450 or 500 watts.

Be careful with Dell. Contrary to reports, they are still using proprietary hardware, and certainly at one stage their PSUs didn't use the standard ATX wiring. Check the colour coding of the main 20/24 pin connector and compare it with that shown in the linked article: http://en.wikipedia.org/wiki/ATX

Any standard ATX power supply will fit a Inspiron 531. The one you mention is overkill, but will fit. Modular power supplies cost a little more, but are worth it for cable management. I've installed one in my Inspiron 531. Just be sure to get one with four SATA connectors and you'll be fine.