Actually, the Dual 2.0ghz G5 (and dual 1.8 i would assume) do best with 2GB of RAM in every benchmark. Some benchmarks preformed the same with 1.5GB, but the majority were best at 2GB (and those at 1.5GB were as high or higher). The 1.6ghz G5 had the largest performance jump at 1.5GB. 2GB showed little improvement for the benchmarks.