settings for postgresql.conf on 7.3.4 vs 7.2.1 and 7.2.4

Dear Guru's,

I have been running the 7.2.x version of Postgresql on about 25 i686 machines
and I have been updating them to the 7.2.1 to 7.2.4. I just started
experimenting with the Severn beta of Redhat ?10? which has rpms for the sexy
7.3.4 of Postgresql.

Well, to handle the heavy load of clients on my dedicated servers running
postgresql I have set certain parameters for the postgresql.conf file as well
as the shared memory.

For machines with 512MB of RAM i set

kernel.shmmax=425000000 in the appropriate place

and in postgresql.conf I set

shared_buffers=48000
max_connections=512
sort_memory=4096
effective_cache_size= 4000
wal_buffers =8
wal_files=4

Now of course I discovered that 7.3.4 does not like "wal_files=4" and refused
to start until I deleted that line. Ok. I did that (I"m easy).

Now, however do I need to change anything else or is this setup fine for a
machine that really does very little else but listen for clients that query
the postgresql server (and then send some files out via tcp in response to
the outcome of the queries).

I am still very shaky as to what the above parameters do. I mostly cribbed the
above settings off documents I found in google all over the internet, sort of
blindly. I am still mostly clueless despite reading Bruce M's discourse on
these parameters etc.

Thank You deeply!

Mitchell