The corespeed of the X1800XT is actually 625/1500, and the RAM chips it uses are actually rated to run at 1.6GHz, so that makes for plenty of overclocking headroom. The core, which runs at 625MHz, is based on a 90nm architecture, which not only will run cooler, but also overclock much better (in theory) than the 7800GTX, because the 7800GTX is based on a 110nm architecture, which uses more power, and runs hotter. Here is an article on theinquirer that claims the X1800XT scores 9100+ in 3Dmark05, however I don't know what their source is:
Here is another article on theinquirer that claims the X1800XT will overclock to 700MHz+:
I again do not know their source, but I do know ATI is going to put up a good fight, and I think it will end up as it always does, nvidia will have the upper hand in some games, and ATI in others. Love your avatar, PZEROFGH. Oh ya, the X1800XT will have 16 pipelines, however I have read in several places, that nvidia and ATI count the number of pipelines differently, and that ATI has claimed that each pipeline acts as 1.3 pipelines, so 1.3x16=20.8, and if that is true, then I think ATI has a slight upper hand. I am not going to buy anything however until it has been released, and there are benchmarks.