hardware raid suggestions

I've been using the adaptec ZCR raid cards in our servers for a while
now, mostly small systems with 3 or 6 disks, and we've been very happy
with them. However, we're building a new DB machine with 14 U320 15K
SCA drives, and we've run into a performance bottlenkeck with the ZCR
card where it just won't scale well. Without going into too many
details, we've tested RAID5, RAID10 and RAID50 on pretty much every
array size from 4-14 disks (raid 50 tests used more drives), using JFS,
reiserfs and EXT3. With every different configuration, performance
didn't improve after array size became greater than 6 disks.. We used
various benchmarks, including pgbench with scale factors of 10, 100,
1000, 5000 and clients of 10, 15, 30 and 45. We've done many other
tests and monitoring tools, and we've come to the conclusion that the
ZCR is the problem.

We're looking into getting an Adaptec 2200S or the Megaraid 320 2x
which have better processors, and hopefully better performance. We
feel that the use of the AIC7930 as the CPU on the ZCR just doesn't
cut it and a faster raid controller would work better. Does anyone out
there have any experience with these cards with postgresql and linux?
If so, would you be willing to share your experiences and possibly give
a recommendation?

--brian