Shopping for hardware

Ok, I asked this on [novice], but I was told it's be better to post it
here...

I've got some money to spend on a new servers. The biggest concern is the
PostgreSQL database server that will "be the company." (*Everyone* uses the
database server in some form or another) I'm looking for hot-swappable RAID
1 on a Linux platform at the least. Are there any vendors to avoid or
prefer? What works best? Am I better off going with a DIY or getting
something pre-packaged?

In terms of numbers, we expect have an average of 100 active connections
(most of which are idle 9/10ths of the time), with about 85% reading
traffic. I hope to have one server host about 1000-2000 active databases,
with the largest being about 60 meg (no blobs). Inactive databases will only
be for reading (archival) purposes, and will seldom be accessed. (I could
probably move them off to another server with a r/o disk...)

Does any of this represent a problem for Postgres? The datasets are
typically not that large, only a few queries on a few databases ever return
over 1000 rows.

The configuration that is going on in my head is:
RAID 1, 200gig disks
1 server, 4g ram
Linux 2.4 or 2.6 (depends on when we deploy and 2.6's track record at that
time)

I want something that can do hot-swaps and auto-mirroring after swap.
Unfortunately, this is a new area for me. (I normally stick to S/W for
non-high end systems)

Thanks!

Jason Hihn
Paytime Payroll