I know I'm late to the party but had a couple simple suggestions for you.
Since you already have a DC with cyclone I wouldn't worry about that setup for the Festool CT.
As far as which vac - either the CT26 or the MIDI to start. I started with the 26 and it's been great. Long time between bag changes - even when running the OF1400 in a table and making a bunch of door stick/cope pieces.
The bluetooth remote is an awesome add on - don't have to bend down or stick my head under a table to turn it on manual mode.
I just picked up a MIDI for projects not in the shop - it's way easier to haul around than the 26. And if it's in my shop I can leave it setup for sanders and the 26 hooked to the router or Kapex. The new MIDI has some more features built in, like bluetooth, which make it even more attractive.
Whichever CT you get I would suggest purchasing a cleaning kit with the bigger (36mm) hose. The tradesman or workshop would do the trick.
The hose alone is more than half the cost of the sets. And I sold the systainer that came with the set which lowered the overall cost even more.
The reason I say get the bigger hose is for use with anything but a sander. The OF1400 would choke up the 27mm hose pretty easily. I also noticed better collection from the tracksaws and Kapex after changing to the 36mm hose.
You already get the benefit of the newer hoses that are 'snag-free' which I think removes the need for some of the other Festool Vac accessories people use to buy.
So here's my suggested list:
Either MIDI or CT26(and add BT remote)
Tradesman or Workshop cleaning kit
And start having fun.