postgres performance optimization

hi all,

I have 1 gb ram on the server

i am doing some performance tuning for postgres server.
some of the configuration changes i have made are

max_connections = 128
shared_buffers = 1048576
sort_mem = 4096
random_page_cost = 2

echo "1073741824" >/proc/sys/kernel/shmall
echo "1073741824" >/proc/sys/kernel/shmmax

are there any other configuration values which will affect the performance.
Also what tool should i use for benchmarking purposes.

thanks in advance,
kailash