Recommended Specs

Hi,

I was reading a lot on the specs that was used by those who runs
postgres.  I was wondering is the a more structured method of
determining what is the required hardware specs?  The project that i am
doing can populate about few millions records a day (worst case).

Based on what i read, this is what i guess

RAM - the more the better
postgresql.conf must be optimized
CPU - not sure if adding more CPU will really help unless i start to
create parrallel insert sessions.
Hard disks - ?? how do i actually check how much space this records take
on the hard drives?
optimized queries is a must
OS? linux? freebsd? solaris?
cpu type? sun sparc? intel? amd?
anything else?

Hasnul