I'm buying a new desktop workstation, and it looks my two best processor options are either a 2.6GHZ 64 bit processor, or a 1.8GHZ dual core. I may be able to overclock to the 1.8Ghz dual core, but assuming I don't, which will give me the best performance in Ubuntu?

If you'll use Ubuntu only for everyday tasks (mail, some editing, surfing); it really won't matter. However, as soon as you get into some heavier stuff, it's more than likely that the dual core will pull ahead. I have an AMD3800 (2.4GHz) and a Core 2 Duo 6600 (2.4Ghz) and I notice little difference when doing some lighter work; but as soon as I start compiling software or editing media, the AMD starts lagging noticeably. Alright, 1.8 Ghz is not 2.4 but it will still be at least as fast as the 2.4Ghz single core - providing we are talking about a Core 2 Duo - an AMD dual core with those specs may actually be slower in many tasks. But that also depends on the rest of your hardware (RAM, motherboard, etc).

I do some audio editing, so I thought dual core might serve me best there. But I also do a lot of everyday tasks. I think as far as money goes, the getting a 2.6 or 3.33 single core might be a better value for me right now. Thanks so much for the reply!