Right now here are your fastest solutions, in order starting with the very fastest:
SiS 655, Dual DDR400
i850E, RIMM4200
i850E, PC1066
SiS 648, Single Channel DDR400
i845PE, Single Channel DDR333
The SiS 658/PC1066 is supposed to be faster still, but I haven't seen any direct comparisons between the 655 and 658.
The Granit Bay is faster than the i845PE sometimes.
i845PE is prefered over the SiS 648 for overclocking, because the fastest, most stable 648 board (8SG667) doesn't have BIOS overvoltage, while many PE boards do.
Price comparison: PC3200 and PC1066 are similar in both price and performance. I believe PC1066 might actually be the cheaper solution.
<font color=blue>Watts mean squat if you don't have quality!</font color=blue>