Here's the kicker...
Power Output: 9 Internal Armour: 0 Explosion Chance: 5
Reactor Size: 2 Reactor HTK: 2
Cost: 27 Crew: 10
Materials Required: 6.75x Duranium 0x Neutronium 20.25x Boronide
Development Cost for Project: 800RP
That's a gas-cooled fast reactor. Output 9 you see. Your ship uses 9 for the PD lasers. So for a 33% increase in size over 1 Tokomak, you get near the same output, BUT with redundancy. Or for the size of 2 Tokomaks, you get 3x the redundancy.
So unless you see a future version where you need 20 power in one burst, the older stuff is still good. Of course, with the Tokomaks, you can design a shell hull (engine, power, fuel supply, etc) and swap weapons, hangars, etc out for different versions.