I thought I would post this as the pc used in this review is very close to the top of the line imac. I included the pc specs below used in the review. Assuming the card in the imac is not the mobile version and the one listed in this review, those who wait are in for an amazing machine.
http://www.guru3d.com/article/radeon-4850-and-4870-review-force3d/9
Mainboard
nVIDIA nForce 680i SLI (eVGA) (1)
Intel X48 (ASUS) (2)
Processor
Core 2 Duo X6800 Extreme (2.9 ghz)
Graphics Cards
ati 4850 and 4870
Memory
2048 MB (2x1024MB) DDR2 CAS4 @ 1142 MHz Dominator Corsair
http://www.guru3d.com/article/radeon-4850-and-4870-review-force3d/9
Mainboard
nVIDIA nForce 680i SLI (eVGA) (1)
Intel X48 (ASUS) (2)
Processor
Core 2 Duo X6800 Extreme (2.9 ghz)
Graphics Cards
ati 4850 and 4870
Memory
2048 MB (2x1024MB) DDR2 CAS4 @ 1142 MHz Dominator Corsair