Sorry was going to put that in but forgot apparently. I'm running 1920 x 1080 at the moment. The 250 is fine for now, it's the rest of my system that is holding it back. With next gen games though it's pretty weak. I figured the newer GPUs will start coming out around fall/early winter though so am kind of thinking my 250 from my old computer will last ok with the new build, NEW BUILD, till then.
Since you are geared up with a X58 build and also taking into account that you are somewhat satisfied with your current GTS 250, i'd recommend getting a single GTX 460 for now.. It'll be a whole lot better compared to the GTS 250.. Also, two GTX 460's in SLI touch upto the performance levels of a single GTX 480/HD 5970.. This much performance comes at lower price, lower heat, lower power consumption and lower noise levels..
At 1920 x 1080 using your new build, it would be appropriate to use a graphics system of about the power of the 5870.
Exactly what that should be is unclear at this point in time.
There are going to be some new and presumably better options arriving in time for the Christmas buying season.
There is talk of new ATI tweaks, and new Nvidia cards . It might pay to wait. Also, the GTX260 is going to put some marketing pressure on ATI so we might see some price adjustments.
My suggestion is to build, using the GTX250 to start with, and see how it goes. No doubt, you will want to do better, but getting some gaming in with the new build will clarify just how much better you need to go.
When you upgrade, it should be by a couple of performance tiers, otherwise you will be disappointed.
A 5870 may be right. Or even a 5970.
Or a GTX480,
Or SLI GTX260(they seem to scale very well)
or... whatever comes next.
Well I found a great combo deal on a xfx 5870 and xfx black edition 850w PSU so I've decided to just bite the bullet and go with that. Thanks for all the help though. I've spent way too much time debating this as it is lol.