Disk arrangement in a cheap server

I will build a cheap server and I'm in doubt about what would the the
best for performance:

1 - everything in one lonely fast 10,000 rpm Raptor HD;

2 - two cheap 7,200 rpm 16MB cache HDs like this:

    disk 1 - system and pg_xlog
    disk 2 - pg_data without pg_xlog
    or a better arrange suggested by you;

3 - The two cheap HDs above in Raid 0.

There will be 4 GB of memory, Fedora 8 and Postgresql 8.3.

Regards,
Clodoaldo Pinto Neto