Tuning Tips for a new Server

Hope all is well. I have received tremendous help from this list prior and therefore wanted some more advice.

I bought some new servers and instead of RAID 5 (which I think greatly hindered our writing performance), I configured 6 SCSI 15K drives with RAID 10. This is dedicated to /var/lib/pgsql. The main OS has 2 SCSI 15K drives on a different virtual disk and also Raid 10, a total of 146Gb. I was thinking of putting Postgres' xlog directory on the OS virtual drive. Does this even make sense to do?

The system memory is 64GB and the CPUs are dual Intel E5645 chips (they are 6-core each).

It is a dedicated PostgreSQL box and needs to support heavy read and moderately heavy writes.

Currently, I have this for the current system which as 16Gb Ram:

max_connections = 350

work_mem = 32MB
maintenance_work_mem = 512MB
wal_buffers = 640kB

# This is what I was helped with before and made reporting queries blaze by
seq_page_cost = 1.0
random_page_cost = 3.0
cpu_tuple_cost = 0.5
effective_cache_size = 8192MB

Any help and input is greatly appreciated.

Thank you

Ogden