Need a System Update: Advice

[one swell foop]

My system is as follows:

Intel q9550 @stock clocks
2x2 Gigs G-Skill DDR 1000 @ 5-5-5-15
EVGA 8800 GTS 512
EVGA 750i SLi FTW
Corsair HX520

I need to give my system more capacity to play current games, not at the higher settings necessarily, I'm under no illusions, but I'd like to be able to play Skyrim on medium or high settings rather than low. My budget is minimal, $200-$300. What should I look at doing? I think the last gen video cards, at the lower price points, would draw too much current for my PSU, and I don't know that they would provide enough of a performance boost to make it worth the upgrade.

I do want to be somewhat future proof, or at least wise in any component choices in any upgrades. I realize that I'm limited by the fact that I have a DDR2 mobo, and that DDR2 is more expensive and provides less performance than DDR3. With the limitations that I have and my lack of knowledge on the last couple of generations of hardware, I;'m not sure what to do.

Help?

 

[tiraides]

If you can, overclock the Q9550 and buy a (used) GTX 560 Ti or HD 6950 (whatever you could afford).

 

[one swell foop]

Will a 520 Watt power supply be able to handle a GTX 560? One of my major worries is getting a card that would necessitate a more powerful PSU, thus increasing my overall improvement cost.

 

[Dangman]

Your current 520HX should work fine with the GTX 560 TI.