The DFI Nforce 4 Ultra-D is the motherboard for you, best overclocker and great value.
Next, that OCZ DDR2 memory won't work with your system since AMD doesn't support DDR2. OCZ does have some high quality DDR stuff though that will perform about the same as that XMS, so it's really a matter of preference. However, OCZ performs better and with more stability than XMS on DFI motherboards, so I'd reccomend the OCZ DDR.
The X1800XT gets beaten by the 7900GT in price and performance, and overclocks more. So your best options would be the 6800XT, 6800GS, 7600GT X1800GTO, 7900GT or the X1900XT (in order of increasing performance, I'd suggest the X1800GTO or faster)