Dividing up a single 250GB RAID10 server for postgres

Hi. We have a server provided for a test of a web application with the
following specifications:

1 Dual core 1.8GHz Opteron chip
6 GB RAM
approx 250GB of RAID10 storage (LSI card + BBU, 4 x 15000 RPM,16MB
Cache SCSI disks)

The database itself is very unlikely to use up more than 50GB of storage
-- however we are going to be storing pictures and movies etc etc on the
server.

I understand that it is better to run pg_xlog on a separate spindle but
we don't have that option available at present.

Normally I use ext3. I wondered if I should make my normal partitions
and then make a +/- 200GB LVM VG and then slice that initially into a
100GB ext3 data directory and a 50GB xfs postgres data area, giving
100GB to use between these as they grow. I haven't used LVM with xfs
before, however.

Advice gratefully received.
Rory