How upgrade 10.6.8 MAC Pro (Model 2007) to 10.7 ?

If I try to upgrade I get a Warning:

"This update requires MAC OS X Version 10.7."

Is there any (other) way to upgrade from 10.6.8?. - For Maverix - the System seems to old (according to the system ID produced in 2007).

I cant believe that Apple provides now upgrade path for a huge / expensive MAC Pro bought in 2008!

Major reason is to use IClaud. I accidentially deleted my MobileMe account data and know there is now way to calander communication back to work!

Paul