logic pro 6 to 9 upgrade

hi all,
my first thread on this forum so hello!!

ive just purchased an 18 month old iMac after my trusted G4 finally gave up the ghost (a relic, i know)...

ive been running logic pro 6 on that machine and my question is, is it possible to reinstall logic pro 6 onto Snow Leopard (if it even works properly) and then uprgrade it to 9 or possibly 8?

I previously installed logic pro 6 but it didnt transfer any of the instruments and so wont play back audio instruments or midi files correctly.

i'd really like to uprgrade, but if i have to purchase i may have to live with logic 9 express for a while as i dont think i'd really use 99% of its new additional features..but any help would be great.

cheers