Hmm.... my system has 410GB, spread over 2 HDs, so it would be tempting to put a larger HD in place of one of the existing ones, & then pass that one along.
OTOH, just bought new machine for youngest daughter, specifically for Photoshop CS4, and there was no room in budget for a 2nd HD - and just KNOW that she will be running out of room by the time winter semester is over....
If lucky enough that it comes to a Decision, might end up having to flip a coin!
(Or else see how Grades hold up....
)