Performance 8.4.0

[Chris Dunn <chris(dot)dunn(at)bigredsky(dot)com>]

Hi,

I would like to know if my configuration is ok, We run a web application with high transaction rate and the database machine on Mondays / Tuesdays is always at 100% CPU with no IO/Wait . the machine is a Dual Xeon Quad core, 12gb RAM, 4gb/s Fibre Channel on Netapp SAN, with pg_xlog on separate Lun,
Could you please provide some feedback on the configuration

maintenance_work_mem = 704MB
constraint_exclusion = on
checkpoint_completion_target = 0.9
effective_cache_size = 8GB
work_mem = 72MB
wal_buffers = 8MB
checkpoint_segments = 16
shared_buffers = 2816MB
max_connections = 32

I have limited connections down to 32 as if I put up higher the machine load average goes through the roof and will decrease performance even more.
In the process of looking at a 4 x AMD 6 core Opteron  machine with 32GB Ram to replace if I cannot get any more performance out of this machine

Kind Regards
Christopher Dunn