RAID Controller (HP P400) beat by SW-RAID?

We've currently got PG 8.4.4 running on a whitebox hardware set up, with (2)
5410 Xeon's, and 16GB of RAM. It's also got (4) 7200RPM SATA drives, using
the onboard IDE controller and ext3.

A few weeks back, we purchased two refurb'd HP DL360's G5's, and were hoping
to set them up with PG 9.0.2, running replicated. These machines have (2)
5410 Xeon's, 36GB of RAM, (6) 10k SAS drives, and are using the HP SA P400i
with 512MB of BBWC. PG is running on an ext4 (noatime) partition, and they
drives configured as RAID 1+0 (seems with this controller, I cannot do
JBOD). I've spent a few hours going back and forth benchmarking the new
systems, and have set up the DWC, and the accelerator cache using hpacucli.
I've tried accelerator caches of 25/75, 50/50, and 75/25.

To start with, I've set the "relevant" parameters in postgresql.conf the
same on the new config as the old:

max_connections = 150
shared_buffers = 6400MB (have tried as high as 20GB)
work_mem = 20MB (have tried as high as 100MB)
effective_io_concurrency = 6
fsync = on
synchronous_commit = off
wal_buffers = 16MB
checkpoint_segments = 30 (have tried 200 when I was loading the db)
random_page_cost = 2.5
effective_cache_size = 10240MB (have tried as high as 16GB)

First thing I noticed is that it takes the same amount of time to load the
db (about 40 minutes) on the new hardware as the old hardware. I was really
hoping with the faster, additional drives and a hardware RAID controller,
that this would be faster. The database is only about 9GB with pg_dump
(about 28GB with indexes).

Using pgfouine I've identified about 10 "problematic" SELECT queries that
take anywhere from .1 seconds to 30 seconds on the old hardware. Running
these same queries on the new hardware is giving me results in the .2 to 66
seconds. IE, it's twice as slow.

I've tried increasing the shared_buffers, and some other parameters
(work_mem), but haven't yet seen the new hardware perform even at the same
speed as the old hardware.

I was really hoping that with hardware RAID that something would be faster
(loading times, queries, etc...). What am I doing wrong?

About the only thing left that I know to try is to drop the RAID1+0 and go
to RAID0 in hardware, and do RAID1 in software. Any other thoughts?

Thanks!

--
Anthony