Upgrade EV 8.0 to EV 10.0

We are running EV 8 on windows 2008 x64 server. we are running exchange 2007.

Plan is to get to EV 10 which will run on windows 2008 r2 x64.

now i know that we have to upgrade to ev 9 and then ev 10.

so do i need to may be upgrade windows 2008 to 2008 r2 so we  have the correct OS.

Then upgrade to ev 9 and then 10.

Please advise.

Thanks

Salman