I'm not sure about the SX / pin head question - that's about the time they shifted. Here's the rest of the changes, though:
Different trampoline (now on 4th version)
Self tacking jib
Revised jib for self tacker
Spin snuffer (vs bag launch)
Different spin cut (now on 3rd version)
Lots of little rigging changes.
Get your wallet out.
It is worth noting that if the boat has been regularly raced, most of the "performance" upgrades will probably have been done. The tramp and boom changes make no difference to the speed of the boat. All of the older Tigers around here have had the tackers and snuffers retrofitted (easy job) and most of the sails get upgraded every few seasons anyway.
I suspect the different spreaders will make very little difference on a well sorted mast. One other upgrade has been the downhaul which is far more user friendly now (easier to pull on) and is a very easy upgrade.