800 DDR2 dual vs 1066 DDR2 single

Hi,

Please could someone enlighten me about some memory questions? If you use your PC for casual gaming (like COHOF and Vegas six type games, IE not the lkatest and greatest) which mode of running memory is better? running 1066 in single channel or moving over to the other sloot and slow it down to 800 dual channel mode, also my motherboard is the ASUS M3N78pro which means the memory drops also from 5-5-5 to 5-7-7 timings for 800mhz to 1066mhz as there is no memory timing settings in the BIOS :-(

Also am I correct in that unganged is faster then ganged?

Cheers
Paul