For resolutions upto 1920X1200, you don't have to get anything more than a HD 4890 or GTX275 for playing the current games (though for some games you would have to turn off/ reduce the AA and AF)...
And for your current resolution, it is an overkill...but as you are planning to upgrade you monitor, then it is fine...
Currently the ATI HD 4890 is the best value card...and I would want to clarify that am not saying it is the most powerful card out there but the best price/performance card...
Currently you can get a HD4890 for about $189 with $20.00 Mail-In
Rebate bringing the price to $169...
HIS Hightech H489F1GP Radeon HD 4890 1GB
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161276
For this price, you can only get an GTX 260 and a decent, cheapest GTX 275 is about $230
And like I said before the HD4890 and GTX 275 are the competitors...