What is the most cost effective hardware for R?

Has anyone got any advice about what hardware to buy to run lots of R 
analysis?  Links to studies or other documents would be great as would 
be personal opinion.

We are not currently certain what analysis we shall be running, but our 
first implementation uses the functions lme and gls from the library 
nlme.  To do one data point currently takes 1.5 seconds on our 3 year 
old sunfire box, and the data points are completely independant so the 
analysis is fully parallelisable without implmenting multi-threading 
within each data point.  We have a reasnoble amount of sys admin support 
in house.  We are an academic institution.  We are looking at spending a 
few thousand to a small number of tens of thousands of dollars.

Any help greatly appreciated


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