Matt
I have the following Festool products; TS-75, OF2200, OF1400 and the associated guide rail adapters.
The "gateway" product from Festool is their track saw. I have the TS-75 only because I honestly do need the extra depth of cut. The TS-55 would have been perfect if I didn't live in a 100 year old house, and tend to start projects with 2" + thick boards. From the track saw most folks branch out and acquire the tools in their lineup that suit their individual need and type of wood working.
Next in my opinion is their routers. I've used a lot of different routers in my life and the Festool's, I have the OF2200 and 1400, are simply the smoothest, most ergonomically controllable routers I've used. The OF 2200 can literally be used with one hand.
The Domino isn't really a unique or special niche tool. Depending on what other tools and jigs someone has, or rather doesn't have, it could be a foundation tool for a small home shop. Loose tenon joinery has been around for multiple centuries and the Domino just facilitates an expedient method to effect it.
You may be selling their jigsaws short. Get a 2" thick billet of a tropical hardwood and put their jig saw to the test roughing out a neck and you might change your mind. I have a Milwuakee jigsaw and the Festool is by leaps and bounds a better tool. The Carvex will be my next Festool product.
The Planex is however a little unique. If you have a lot to sheet rocking to do, or redo, it would be very nice, if it works as advertised. I think though that you really mean a power planer though and not the Planex.
You're in a pretty good situation if you're "making do" with a Fein Vac. I have the Fein Turbo II and I see no reason to get a Festool vac myself.
Let your work dictate your needs and so far, from your posts, It seems as if you really just need a track saw, Festool or not, to do the initial breakdown of material and then final cut to size.
PS.
Get a sliding table saw someday Doc'. The best engineered insurance for your hands, is to never have the ability to get them near a blade.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)