Postgresql system requirements to support large databases.

We are looking at implementing a large Postgresql database (50GB -
100GB) and are wondering if there are any limitations or problems for
a database of this size running on 32-bit architecture.  I have seen
some older posts where it appears that Postgresql seemed to have
performance problems when the database reached 5GB, and it was
recommended that 64-bit architecture be used.  Is this still true with
Postgresql version 7.4?  This will be out first experience with
Postgresql and we are needing to get some ideas of what system
requirements a database of this size will require.  Since the machines
that we have are all 32-bit, we would like to know if we will need to
go to 64-bit.  Any comments or suggestions??

Thanks in advance for any help.