I wouldn't sell your self short: get dual processors, true raid,
hotspare, copper gigabit. Your backup system is too important to penny
pinch and is the first domino that needs to be stood up in a disaster.

>From what I've seen Veritas software purchasing comes in Tiering with
the same price for 1-2 processors; next tier for 2-4, etc. 

How much money are you really going to save?   In one year (or less) or
backup environment may grow and you'll end up needing more processing
power.