most bang for buck with ~ $20,000

I've asked for some help here a few months ago and got some really helpfull
answers regarding RAID controllers and server configuration. Up until
recently I've been running PostgreSQL on a two year old Dual Xeon 3.06Ghz
machine with a single channel RAID controller (previously Adaptec 2200S, but
now changed to LSI MegaRAID). The 2U unit is from a generic vendor using what
I believe is a SuperMicro motherboard. In the last week after upgrading the
RAID controller, the machine has had disk failure and some other issues. I
would like to build a very reliable dedicated postgreSQL server that has the
ultimate possible performance and reliabily for around $20,000. The data set
size is only currently about 4GB, but is increasing by approximately 50MB
daily. The server also requires about 500 connections and I have been
monitoring about 100-200 queries per second at the moment. I am planning to
run FreeBSD 6.1 if possible, but I am open to any other suggestions if it
improves performance.

I am considering a setup such as this:
- At least dual cpu (possibly with 2 cores each)
- 4GB of RAM
- 2 disk RAID 1 array for root disk
- 4 disk RAID 1+0 array for PGDATA
- 2 disk RAID 1 array for pg_xlog

Does anyone know a vendor that might be able provide such setup? Any
critique in this design? I'm thinking having a 2 channel RAID controller to
seperate the PGDATA, root and pg_xlog.

Sincerely,
Kenji