The 7800GTX is about 2x as fast as a 6800U in some tests, so a dual core 6800U should be compairable, but a tremendous price concidering you can hardly find a 6800U under $400.
4x SLI would be cool but a big pain upgrading 4 cards.
it would be nice if they made some sort of sli, exept it was 2 whole computers working together, so 2 3ghz computers =6ghz, cheaper than dual core it would be.
better stop going on about that, its going off topic.