~400 TPS - good or bad?

Hello,

We are trying to optimize our box for Postgresql. We have i7, 8GB of
ram, 2xSATA RAID1 (software) running on XFS filesystem. We are running
Postgresql and memcached on that box. Without any optimizations (just
edited PG config) we got 50 TPS with pg_bench default run (1 client /
10 transactions), then we've added to /home partition (where PGDATA
is) logbuf=8 and nobarrier. With that fs setup TPS in default test is
unstable, 150-300 TPS. So we've tested with -c 100 -t 10 and got
stable ~400 TPS. Question is - is it decent result or we can get much
more from Postgres on that box setup? If yes, what we need to do? We
are running Gentoo.

Here's our config: http://paste.pocoo.org/show/224393/

PS. pgbench scale is set to "1".

--
Greetings,
Szymon