And since your going to be mostly gaming you might want to consider getting a a duel core, like the E8400 or E8500.
However future games will probably start taking advantage of the more core power quads give. And an overclocked Q6600 is a pretty nice gaming chip itself.
And then for your graphics card.... If you have a high budget then go with a 4870x2, but if its not that high, go with a 4870 right now and then you can crossfire another when you get the funds.
If you really want to go nvidia, then for a higher-end mobo get the 780i, and for more of a budget board take a look at the 750i.
The x48 and x38 chipsets provide CrossfireX at 16x speed on both of the PCIe 2.0 slots.
The p45 will provide 16x when using one card in your PCIe 2.0 slot, but when you crossfireX cards it will then change to run both cards at reduced bandwidth of 8x.
Technically you won't take a huge performance hit with 2 8x lanes, as opposed to 2 16x. But you will lose some FPS, especially at the higher resolutions. And I figure if your going to buy a $250+ card you might as well get all you can out of it.
And since you will be gaming at 1920x1200 with that monitor, I imagine you will want to crossfire if not now, a little later on when funds allow.
However if you are pretty certain you will never want to Crossfire/SLI, a p45 board would be a good choice.
Well if you're gonna go with that nVidia board you may want to consider getting a 9800 GX2. As to if you should choose that over the 260 it's going to depend on what games you want to play and at what resolutions since the 9800 GX2 doesn't always scale well, but when it does it's awsome. Personally I'd say go with a good x38 board or if that's not in your budget then a good p45 board. Then go with a single Radeon 4870 now and drop in another one latter to run in crossfire.