Thats a tough choice since the upgrade cost is similar to just getting a newer kit. More or less just looking at the budgeting and what makes sense to you, if your planning on riding lots more in the future, I would point you at a newer kit, but if you don't ride quite as much, then just upgrading and saving a few bucks would be the ticket. I love pushing these things to the limits so there is still a gap between a fully updated 13 kit vs a 16, but if your more of a casual rider, most likely wouldn't notice the little gaps.
Track goes that much better in the deep and makes the trail a world of difference. TSS is also such an impressive upgrade especially if you have any desire to jump, pound the whoops or race the trail.