postgres on a beowulf? (AMD)opteron?

Has anyone run postgres on a beowulf system? 

I'm shopping for a new server.  One candidate would be a
quad opteron (64-bit AMD "hammer") machine.  Another approach might
be a beowulf of single or dual opterons.  I imagine the beowulf
would be a bit cheaper, and much more expandable, but what about
the shared memory used by the postgres backends?  I gather that
postgres uses shared memory to coordinate (locks?) between backends?

I have a smallish DB (pgdump|bzip2 -> 10MB), with ~45 users logged in
using local X(python/gtk) postgres client apps. 

Will the much slower shared memory access between beowulf nodes be
a performance bottleneck?  

[Next question is: has anyone used postgres on an opteron at all??]

-- George
-- 
 I cannot think why the whole bed of the ocean is
 not one solid mass of oysters, so prolific they seem. Ah,
 I am wandering! Strange how the brain controls the brain!
	-- Sherlock Holmes in "The Dying Detective"