Upgrading my video card?

[babtothebone]

So, I recently bought Skyrim for the PC so I could download mods for it. It checked my computer and gave me a default of "Ultra High" graphic settings. I was pleased to see that, started my game, and it lags terribly. I'm assuming I should upgrade my graphics card to play at this quality? I also have trouble playing Just Cause 2, even at low settings. My current specs are:

Proccesors: AMD Phenom II X6 1100T Processor 3.30 GHz
RAM: 8G
OS: Windows 7 64-Bit
Graphics Card: ATI Radeon HD 5670

Edit: Just set it to the lowest resolution and the lowest quality graphics, and now it runs almost as if sped up. It might not be, and it might be just because I'm comparing it to before, but I still don't want to have to run Skyrim at this quality. I'd like to run it at the highest quality on the large resolution, so.. yeah.

 

[babtothebone]

HD 7850s in Crossfire can beat a single GTX670 or a HD 7970.
From the games that you play, I don't really see the need for a high end GPU. But it's your choice.

Okay. If two HD 7850s in Crossfire can trump the single cards, then I'm definitely going to go through getting the HD 7850.

Most games that I play won't really take a high-end GPU, but I'm also worried about future games I may get. Additionally, Skyrim has a lot of mods that make it far more graphic-intensive with DOF, high-quality textures, etc. It's the one I'm most worried about.

Thanks everyone for the help! I know it took a lot, but I've decided what to do now. I wish I could select multiple best answers, because everyone has been so helpful, but I can't.

 

[babtothebone]

Best answer selected by babtothebone.

 

[Gman450]

Yes, Skyrim will get more intensive, but I don't think it'll be too intensive for a HD 7850 to handle.