at this time crossfire outdoes sli due to nvideas terrible sli drivers.
the ati/amd crossfire drivers are good and perform well on games ...
the nvidea turtles should have its sli drivers updated by february
and then sli will blow away crossfire ..
If your budget is $1000 and the Intel build is at $609, swap out that 8500 for a 8800gts 320mb for an additional $200, then take the rest of your budget and get a Q6600 for an additional $100. Windows XP pro: $90. Exchange that 1GB for 2GB of GSkill for $50. Tons of power and potential.
8800 gts 320mb: $270.00 (minus the $80 for that 8500, that's only a $200 difference)
Q6600: $280.00 (minus 172.00 for the E6550=only $108 difference)
1gb to 2gb upgrade = extra $50 (optional for later)
XP Pro: $90.
Just think about the massive upgrade that you can get and still come in on or just $30 or so over budget. Not bad, eh?