I have the original ICS 5HP SawStop with 52" rails. I don't yet have a jointer/planer, but have looked at the A3-31, and will likely get a machine like that when I do get one. I think the order you pursue should reflect what you are building and what the current limitations you're facing are.
For me, that was the SawStop first. I'm an intermediate woodworker, and I make a lot of things out of sheet goods. My previous saw was a Bosch 4000 portable, and while it was pretty nice for a portable saw, I found myself trying to do fairly scary things on a tool that was really inadequate for the size of material I was working with. I decided to solve both issues with the 52" Sawstop - big enough to handle large workpieces, and less likely to hurt myself both in that the saw is big enough to safely hold my workpiece, and if I do something really dumb, there's an insurance policy.
About 9 months after getting the SawStop, I got a TS75 and a big piece of pink foam. This has changed the way I work with sheet goods. Now my rule of thumb is if the piece I'm working with is 1/3 of a sheet or less, it goes on the table saw. If more than that, it goes on the floor with the track saw. My cuts are better - no more table saw wiggle, and I can do it by myself.
I looked briefly at sliding saws after reading comments like the ones in this thread, and I confess I must be drinking the wrong Kool Aid. For a part timer like me, the cost, shop space, and the fact that I still have to lift and move the whole piece of wood up onto the slider make it not better than the combination of table saw + track saw, at least for what I do.
I will say that now that I have the track saw, I could have gotten away with the 36" rail version of the SawStop. It wouldn't have made a lot of difference in my shop, but for people where the 16" saved would matter, that might be a good compromise.