I went from pro audio 9.0 to sonar 8 and it was a big jump as far as features and learning curve.
After sonar 8 I've gone through every single X series (sonar x1 thru platinum)
and its been well, well , worth it.
check out some videos on you tube and if you can swing it, grab a groove 3 video (Sonar platinum)
but I believe between you tube and cakewalk(also has a great stock of videos on site)
start here:
https://www.cakewalk.com/CakeTV/SONAR-University you will be pleasantly surprised how much your world will change.
The problem with pro audio 9 for me was I had trouble running it in windows 7 (ya I tried to open it)
even with compatibility settings it was missing some features.
but all your old projects should work fine but I don't need to tell you that because these other guys
have covered that nicely.
Welcome to the best forum on the web.