There are a couple of ways to go with this and it's going to be up to what you eventually want to do.
You can get what's just enough or you can get more that what's just enough in case you change something else down the road , like your monitor. If for some reason 6 months or a year from now you decide for whatever reason to go with a larger monitor with a higher native resolution you would already have the video card for it.
I'm sure that right now you are fine with the monitor you have but you don't knowe what can happen or what opportunity will come about that could bring you to getting a different monitor. I like the idea of getting the most that you can for the available money that you have.
EVGA 01G-P3-1561-AR GeForce GTX 560 Ti FPB (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card
$224.99 and a $25 rebate makes it $199.99 and free shipping.http://www.newegg.com/Product/Product.aspx?Item=N82E16814130604
I think that this would be a great card to pick up and it comes with a lifetime limited warranty. It also comes with a small factory overclock so as you have said you don't overclock much , then with this card it comes that way already.