hardware for a server

Hello.

It's time to get new hardware for a server that will run both
PostgreSQL and Apache.
The workload will be similar to that of your standard "PHP forum"
(most selects and logging of stuff that has been read)

The modell I'm looking at right now is

2x Xeon E5520 2,26 GHz 8 MB (8 cores in total)
24 GB 1066 MHz DDR 3 ECC (or more)

When it comes to a RAID controller I have the choice of:

3Ware SAS 9690SA-8i 512 MB BBU
Adaptec SAS Raid 5805 256 MB BBU
LSI MegaRaid SAS 8708 128 MB BBU

Any advice/experience on what raid controller to pick? The 3ware has
the most memory and I've read some good reviews on that one.
The OS will be CentOS 5.4

When it comes to harddrives I think my best optins is to use

* 4 discs (raid 10) for the database

and

* 4 discs (raid 10) for OS, xlog and other data (images,avatars etc.)
or more likely:
* 2 discs (raid 1) for OS/xlog and
* 2 discs (raid1) for "other data"

When it comes to choosing the acctual discs I guess this would be
appropriate to use:
"other data": Barracda ES.2 1000 GB (SATA) to get a a good GB/$ ratio.
OS/xlog : Barracuda ES.2 500 GB (SAS)
DB: Cheeta 15K.6 146 GB (SAS) (The 300 GB would be better if I can
find some more money)

This of course gives me a headache when it comes to keeping spare discs.

The other option would be to use OS/xlog and DB on Barracuda ES.2 500
GB (SAS). I have no idea what that mean to the performance. A lot/
barely noticable?

Any comments, advice on this kind of setup?