i have just upgraded to windows 7 and i was running sonar six, on xp before, what is the best upgrade i can get for windows 7 ?

Sonar Platinum is the best upgrade and will run on Win7.  The other versions of Sonar (Artist and Professional) will also run on Win7.

Zen Studio
i have just upgraded to windows 7 and i was running sonar six, on xp before, what is the best upgrade i can get for windows 7 ?

If you're asking for the latest update for Win 7, it's service pack 1. when you say "best upgrade", do you mean upgrading to Windows 10? (since you just "upgraded" to Win 7)
 
Not quite clear on what you're asking.
 
Here's a link to Win 7 Service Pack 1 (Update):  http://windows.microsoft.com/en-us/windows/service-packs-download#sptabs=win7
 
EDIT: Oh yeah.....there's also SONAR upgrades.....lots of upgrades available.....lol