please help recommend video card for this setup

Hi,
I have HP Pavillion p6608f. It has 250W power supply, Core i3 540@3.06Ghz, 4GB RAM, MS-7613 (Iona-GL8E) motherboard. This mobo has a PCIExpress 16x slot. I currently use the onboard graphics (Integrated Intel H57), but I am considering to purchase a new video card. I understand that I may have to get a new powersupply if i wanted something more expensive. My budget for the card would probably be around 250. Alot of the games ive tried like Deus Ex are really choppy (basically unplayable) even at low settings.

Can someone recommend a video card given this setup? Are cards around the $250 range considered to be too powerful in this system configuration? Should I consider something lower? For example, would it would be a waste if I purchased a 560ti 448 with a new power supply?

Thanks!

What resolution is your monitor?

It is 1920 x 1080

You might be able to get away with an HD 7750, but I think even that could be a stretch on a 250W PSU. You may have to upgrade the PSU in order to upgrade your graphics card. I certainly wouldn't get anything more powerful than an HD 7750 given the rest of your specs.

I know someone with a similar HP desktop with a 250W PSU and they added a Radeon HD 6670 DDR5 for gaming on a 1920x1080 monitor and it works fine for them. I'm confident that a 7750 would work in your computer if you want to spend that much.

I am fine with buying another power supply. Given that I will get 650 or higher power supply, what your recommendations change?

Did you guys suggest at most a 7750 because of the cpu or what other limiting factors?