Advice please: Upgrade mail server or service contract?

Folks:

My main mail & list server (rivendell) system is getting near the end of
it's current maintenance contract.

I have to decide if I want to extend the service contract or get a new
system.

I'm thinking a new service contract will probably be $300 or so.  A new
system would be around $800.

The system is kind of old ... and VERY loud.  It's also a bit on the
flaky side (nothing I can pin down though).  It's a Dell PowerEdge 600SC
with 2.4ghz P4, 160gb of mirrored IDE DASD, 640mb of ram, and a SCSI
tape drive.

A new system would probably be something like a Dell PowerEdge SC430,
2.8ghz P4 (ht), 160gb of mirrored SATA DASD, 768mb of ram, and the same
SCSI tape drive.

So the question is: Should I extend the service contract or get a new
system?

Thanks!

david