Prius vs Prius: which is a better deal?

[p8712]

Black wrote:
[quote=bfd]
Make sure both cars come with a spare.

I have used 2 or 3 Priuses and have been impressed with the amount of cargo room.... but still, I don't see how you're going to fit a second car in there.
Can they be added by a do-it-yourself 'er?