The Nec 2490wuxi2 is a nice monitor is mostly meant for professional use or "pro-sumers" like me. I haven't really read any reviews of it, but the original version the LCD2490WUXi is a phenomenal monitor for graphics professionals due to it's color accuracy and top notch nornal gamut backlighting. I have it's "bigger brother", the LCD2690WUXi.
The higher input lag is due to the extra color processing to improve color accurarcy and to create uniform colors on the screen. This takes a bit of time and is the reason why it's predecessor; the LCD2490WUXi was so highly regarded by graphics professionals. I'm sure the WUXi2 is good as well, but I haven't read any reviews; I don't want any incentive to add another expensive monitor along side my LCD2690WXi and Planar PX2611w.
If you are looking for an alternative 1920 x 1200 monitor, then I recommend the Planar PX2611w which has been tested to have less than 8ms of input lag by
ToastyX in www.hardforum.com. It uses the same H-IPS panel as the NEC LCD2690WUXi, but lacks the extra electronics for improved color accuracy and color uniformity found on NEC's WUXi series.
Here's a link to the Planar PX2611w...
http://www.provantage.com/planar-systems-997-3497-00~7PLNR049.htm
As for the GTX 480, I don't know how powerful it is compared to the HD 5970 (I do not need any enticement at this point in time). But the HD 5970 can be used to play games at 2560 x 1600. The exception would be Cryis.