I ran all those services at once to try out the performance, and I have to say turning on SABnzbd took the biggest hit. SSH'in for example was just dam slow. I am not sure how you manage to run all those with XBMC on as well. I was using raspmc distro, not sure that makes a huge difference.
Use OpenElec it's a dedicated distro for this. If you try setup those things individually as you would on a desktop you are going to have a bad time. And yes SABnzb is slow as hell extracting but all her TV shows download and extract in the middle of the night.
