To crossfire X48 is certainly the way to go, but for single card setups, the difference will either be null or negligeable. Yes the bandwidth doubled, but most cards didn't even use the full 1.0 bandwidth so no difference there.
In CF it's different since the cards use the PCI-E bus to communicate with each other, that is why there is a gain there.
Granted - however the reason i ask is as follows.
In comparison to both my current results and the results i had with my 3870
My SME3.0 scores were a bit odd. both suffered about 20-30FPS lower on the Canyon flight score when compared to other systems running either P45 or higher shipsets had a much better canyon flight performance.
My assumption is that the Bandwidth of the P35 PCI Bus is limiting.
Or would it be the DDR2 800 RAM.
Granted my next purchase is the second HD4870 and the reason i got the ASUS Rampage is that it runs 16x16 and not 8x8.