Upgrading from 5 to 6

I'm going to upgrade from 5 to 6 soon and would like to know if it actually upgrades 5 to 6 or installs a seperate version? Is there any preperation I should do? I have a two year old iMac with latest OX and I'm currently running Win XP 64 in the VM and use coherance mode.
Thanks,
Tom

 

Dont do it! I just the 6.0 upgrade and it just gives you eye candy. My speed was gone, programs took 10 seconds to open. I even reinstalled tools and tried to configure the memory I ran 1 gig up to 3 gig of my 4gigs and nothing it ran slow regardless

 

Thanks for the information. I already bought 6 but won't install it untill further notice.