Hardware advice

Hello..

I'm waiting for my new system , and meanwhile , i have some questions.
First , here are the specs:

The server will have kernel 2.1.19 and it will be use only as a postgresql
server (nothing else... no named,dhcp,web,mail , etc).
Postgresql version will be 8.2.
It will be heavily used on inserts , triggers on each insert/update and
occasionally selects.

System: SuperMicro 7045B-3
CPU: 1 Dual Core Woodcrest ,2.66 Ghz , 4Mb cache , FSB 1333Mhz
RAM: 4 Gb (4 x 1 Gb modules) at 667Mhz
RAID CTRL: LSI MegaRAID SAS 8408E
DISKS: 8 x SATA II 7200 rpm , NCQ , 8 Mb cache with Supermicro 8
Sas enclosure

Based on the needs , i'm planning an update of the drives to 15.000 rpms
SAS. (pretty expensive now)

Question 1:
The RAID layout should be:
a) 2 hdd in raid 1 for system and pg_xlog and 6 hdd in raid10
for data ?
b) 8 hdd in raid10 for all ?
c) 2 hdd in raid1 for system , 2 hdd in raid1 for pg_xlog , 4
hdd in raid10 for data ?
Obs: I'm going for setup a) , but i want to hear your thoughts as well.

Question 2: (Don't want to start a flame here..... but here is goes)
What filesystem should i run for data ? ext3 or xfs ?
The tables have ~ 15.000 rel_pages each. The biggest table has now
over 30.000 pages.

Question 3:
The block size in postgresql is 8kb. The strip size in the raid
ctrl is 64k.
Should i increase the pgsql block size to 16 or 32 or even 64k ?

As soon as the system will be delivered , i'm planning some benchmarks.

Regards
Alex