Low cost HTPC/Mail/All purpose server

BACKGROUND: I have two PCs which have died recently (one was about 5 years old, the other was only 2 years). Not sure what's wrong with either and I'm a bit nervous about trying to salvage parts and introducing possibly faulty hardware to a new system. Given the age of the components would it be worth testing/salvaging them?

I would like to make use of the cases if possible but I'm concerned the older cases may not have sufficient airflow to service newer parts. The younger case is an Antec SLK1650B . I'm sorry but I don't know the model number of the older case (but it is also an ATX Mini Tower). I was thinking I might use the Antec SLK1650B as a normal desktop PC for uni work and the older case for a low power server . Good/bad idea?

APPROXIMATE PURCHASE DATE: No rush. Wouldn't mind sometime this month .

BUDGET RANGE: AU$400 - 500 (flexible )

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Mail server, file server, MythTV backend, web server

PARTS NOT REQUIRED: Keyboard, Mouse, Monitor, Case (depending on the feedback I get), Optical Drive (the one I have is SATA),

PREFERRED WEBSITE(S) FOR PARTS: MSY (Australian retailer)

[url=http://www.msy.com.au/Parts/PARTS.pdf][/url]

PARTS PREFERENCES: Good quality parts. I prefer quality and reliability over cheap components. I prefer Intel.

OVERCLOCKING: No

SLI OR CROSSFIRE: No

MONITOR RESOLUTION: NA

ADDITIONAL COMMENTS:

1. I would like a quiet PC
2. If people recommend I buy a new case I'd like it to be small.
3. I'd like low power consumption products

Your opinions and thoughts are very much appreciated!

Thanks for the reply . I will review those components and let you know how I go.