DB Performance

I need to find a way to increase performance on my server.

We are currently using postgres as a back-end to our web-based corporate
wide application. The application is used for everything from collecting
large amount of data, updating current data and creating large reports based
on this data. At this point we have about 3000 users on the system  and this
is going to grow rapidly.


We are running apache, mod-perl, sendmail, and postgres on our server. The
machine is a dual 900Mhz processor with 2 gigs of ram, and fast 10k raid
drives.

I have set the shared memory on the machine to 512MB.

Postgres is configured as follows:

sort_mem = 128672
shared_buffers = 60800
fsync = false


We will be purchasing new machines to split off the web server from the
database server.

What else can I do to help performance?
Will a beowulf cluster help to increase performance?

Any suggestions would be greatly appreciated.

Thanks,

Gary