Slow Performance

I have a monster db server, with 2 gigs of memory all for PostgresQL
7.0.2.  The machine is a PIII - 800 Zeon with 10,000 RPM SCSI drives.  I
have a database with about 8 tables with over 1.5 Million rows.  It's
running slower than I like when running simple sql queries on one and
two tables.  When I look at postgres I notice it's only using 80 megs.

1) Would increasing the memory postgresql is using increase performance?

Here's my current command line:
/usr/local/pgsql/bin/postmaster -S -D /usr/local/pgsql/data -i -o '-F'
-B 2048 -N 1024 &

2) Are there any other suggestions to how I run Postgresql to increase
my performance issues?

TIA,

Gavin