Wow! Glad you came through for your client. For this very reason I've not done squat to my system since Sept. 2016.
I've decided just to go with what I have for awhile. No upgrades, no new plugins, nothing...
 
If I can't make a song with what I have, I can't make a song. But knowing that my system won't let me down is the most important thing and with software trying to work with third-party plugins can be a nightmare.
 
Sonar started crashing when side-chaining so guess what...I don't side-chain :)
Love Sonar!