You could just torrent 10.6, since you are looking to re-install everything anyways.
It is Free
It is not stealing as you made the original purchase
You own a mac
Solves your problem
No need to learn a new O/S
You have 10.8 DVD as backup if it goes wrong
P.s. doing a little research, the process might be a little more complex than installing Ubuntu but just remember after the Ubuntu install you still need to mess around with Wine.