That's an easy one to get tripped up on. Fell for it more than once myself.

I went through and did installs of Ubuntu, Kubuntu and Xubuntu (all 8.10 64bit) to gauge the benchmarks on my Opty 185 to get a comparison and check for any weirdness.

Ubuntu - 2389/5503
Xubuntu - 2383/5535
Kubuntu - 2401/5617

(all at 2.86 with 6.2.15 64bit and completely fresh installs)