The Sommerfeld stuff can be used on its own, it is not ONLY good to use in his system. I have the offset T & G bit and the Cabinet bit set, the router table(older version), the pocket screw set up, the cabinet arched and straight templates, plus a bunch of other stuff and I rarely use it all together unless I am making cabinets.
If you are going to make cabinets you may as well use his system it is the best by far. If you can afford it I would buy everything he sells. People have been complaining that the new aluminum top on his newer style table is not flat, but a buddy just got one and it was flat to within .001 over the entire thing, seems flat to me.
That Katie jig has been out at least 9 years that I know of it's not new at all. I guess he pushes the Triton router now, but you do not have to use that router.
I am a big fan of all the Sommerfeld stuff. Festool is a system too. Again you do not have to have everything in Sommerfelds system to make it work.