Video card for Skyrim

So i spent about $500 on a cheap gaming rig a couple months ago and now I'm looking to upgrade for Skyrim. Currently my specs look like this:

- AMD Athlon II x4 (Quad Core) 640 3.0GHz processor
- 4GB DDR3 1333MHz Memory
- 1 TB Hard Drive
- Nvidia Geforce GT520 1GB
- PSO 300W Power Supply

I'm barely able to run Skyrim on low settings with this current build. I want to upgrade my graphics card, first and foremost, and i'm looking to spend around $150. I've also looked into adding another stick of 4GB DDR3 ram.

I was hoping for any suggestions I can get because I would like to be able to run Skyrim on Ultra.
 
Your going to need a PSU upgrade to get anything spectacular. But a Radeon 6670/ GT 440 could keep you out of trouble.

if you had a 550W PSU I would say something on the lines of a GTX 550 ti/ Radeon 6790.
 
Yep, get a 500W+ PSU for ~$50 and a graphics card with the rest of the money. You won't see any benefit from extra RAM
 
Back