best OS suggestions / ease my doubts

Hello,
Just a quickie. We are planning an upgrade from 7.1.3 to 7.3. Since we
have to bring down our production server to do it we are planning on
killing all the birds with one shot. We are running RH 7.1 and were
planning on using RH 8. After reading a little bit recently here and
there and installing RH 8 on a simple mail server, I'm getting a little
nervous.
We have a database dedicated Dell 6450 quad Xeon machine with 6gig ram.
We have had frequent bounce buffer errors and have to run the enterprise
kernal rather than the smp kernel to recognize the full memory with RH
7.1. I realize this is more of an OS question, but I want to provide the
optimal OS environment for our Postgres intallation and you guys are the
most attuned to those issues.
Anyone got any real case based suggestions using similar hardware
config, Postgres 7.3 and a more recent linux?
Many thanks!
--
Bill MacArthur
Webmaster
DHS Club