What sort of desktop computer should I get for EMAN2 reconstructions

Suggestion as of 12/1/2011

Obviously for large jobs you're going to need access to a linux cluster, but regardless you will still need a desktop workstation.

A complete answer to the question depends a bit upon your budgetary constraints, or lack thereof. As you are probably aware, at the 'high end', computers become rapidly more expensive for marginal gains in performance. Generally speaking, we tend to build our own Linux boxes in-house rather than purchasing prebuilt ones, both as a cost-saving measure, and to insure future upgradability. Then again, there is nothing wrong with most available commercial pre-build PCs as long as you get the correct components. For a minimal cost-effective workstation, I would suggest:

hope that helps.

Note that these are just my own personal opinion, and do not represent an official recommendation from anyone other than myself. Your mileage may vary.