[CentOS] Adding RAM

I have a server running Centos 4.7 32bit.  Will moving from 4Gig of
RAM to 8Gig do any good?  Since its 32bit I assume it will only be
able to address the first 4Gig not?  When I installed CentOS I did not
do anything special to enable using more then 4Gig if thats required.
Exim, spamassassin and Clamd seem to be the biggest load on this
machine.  My biggest bottle neck is disk I/O anyway.

Wish I had installed CentOS 5.x 64bit way back when but some of the
software I was using at time listed support for it as beta.

Matt