Thanks for your answer about video card -- that is encouraging. 

How much RAM should be installed on each render workstation
(rendercow)?

With Linux, it is possible to configure a diskless workstation (no HDD). 
Would a render workstation (with enough RAM) be able to operate
without an installed HDD ? 

I already have about 12 workstations that were configured as a SETI
farm -- that is, they were running the Berkeley SETI-at-home distributed
computing cient software. 

I expect that when my render farm has been configured, I will be offering
some free render time to Renderosity members for a few months. 
This will help me perform a system test, test my automated submission
interface, measure the overall performance, and do a general shakedown
and reliability test. 

--
Martin