Simmultanous Connections

Our company is converting to either PostgreSQL or MySQL. We are leaning
toward postgresql, but,
we still have a few question about PostgreSQL's ability to handle the
traffic at our shop. I would
appreciate any help you can give me.

1. If a user runs a JAVA program that opens 3 postgresql databases, is
that 1 connection or 3 connections?  Is there a connection when the
database is opened, or only when the  frontend passesthe job to the backend?

2. I read the Q&A on  PostgreSQL and I said that more than 32
simmultanous connections could
drain my resources. Can someone tell me  how much resources are used per
connection?

3. If I have 90 teachers posting grades at the same time (grade posting
has 5 databases open at   once) and 25 administrators poking around in assorted databases
looking at this and that bit of    info. Will PostgreSQL handle this much activity?  This is a
resource list : Our Linux boxes are    from 166 to 450 Mz, 128 MG of RAM and 6.2 to 13 GIG of Diskspace.
The databases will reside    on the Linux boxes and the users access them over Windows work
stations. The applications are     in JAVA.


Thanks in advance for any help you can give me.
Jude Weaver.