Any reason you are using xbmc and not Boxee?? I have found Boxee to be much friendlier, easier to configure and it populates your movies much more efficiently.
I just read a bit about this on the boxee forums. Most people are happy running ubuntu on their single core Revo, but that doesnt support netflix. Next would be a Netbook rev. of Win7.
But most people say if you want the small footprint of a Revo, spend the money on the Dual core. Seems people have no issues with that. But then you get into the price range of a mobo/proper cpu combo. All depends what you're looking for in the end.