If you want to overclock, I wouldn't recommend corsair...especially not value RAM.
G.Skill
OCZ Platinum Rev 2
PQI Turbos
Patriot XBL series
G.Skill and OCZ right now are basically the two best OC'ing modules you can get....at around $300 for 1gb I'd expect nothing less
Overall the X800XL and 6800GT are really close in performance, but the price is the main factor here. Damn near $100 cheaper for the X800XL so I'd say that's the way to go.
Other than that frontsides suggestions of the ABit board is good for OC'ing, also DFI lanparty boards are really good.
3000+ or 3200+ either or will give you good OC'ing potential, I'd suggest winchester core. They run cooler and have a tendency to OC a little better, but with good cooling you could get a nice OC on the newcastle as well.
That would be the first time I would have seen corsair get that high. They aren't the best for OC'ing and if you go to xtremesystems.org where people hold world records for OC'ing you'll never see corsair among those records.
Also to my knowledge corsair doesn't use brainpower PCB which has some benefits for higher OC's coupled with samsung TCCDs
I'm surprised the samsung TCCD's would even want to function that high with that amount of voltage. Generally it's the BH-5's that flourish with 3.2v and higher.
But based on the assumption of regular 2.6-2.9v settings within a BIOS, G.Skill and OCZ will pretty much always OC higher than corsair