Hi Konrad,
I completely understand users not wanting to upgrade because of the investment in time esp if they are heavily involved in production and can't afford any downtime. I've seen studios using ancient versions or obsolete software/hardware just because they are used to it. Nothing wrong with it - musicians still use instruments that are 60-70 years old and don't even play that well after all :)
Anyway regarding X1 my honest advice is to move on and upgrade. There are literally thousands of bugs that have been fixed since then. You seem to have a decent system set up. I can't see why Platinum won't run leaps and bounds better than X1 on your rig. In fact with all the optimizations I think you will find that it saves you valuable time since many common operations are much faster.
Regarding your bugs there were many fixes to snap etc since X1 so if its bugging you (pun intended) upgrading will address this. We haven't heard reports of these issues in Platinum. You shouldn't have to do any setup to your plugins. Installing SONAR won't change that - it will just rescan your plugins using the newer improved/faster scanner. The only thing you may need to tweak there is if you were using custom plugin layouts. You should be able to save and restore those however for the most part. If you want to be really cautious do a system image so you can restore it if for some reason you need to roll back. If you have any issues in Platinum that are genuine bugs there is a high likelihood they will be fixed soon, as compared to X1 which would be never!
Good luck.