I want to move over to kalk, and set up a copycat of the Tunze topoff kalk reactor system, though I've been dosing 2 part through BRS dosers on timers for the better part of 2.5ish years with success.
I'm not sure that kalk would be able to keep up, but now that I'm going through about a gallon a week instead of a gallon every 2 weeks (slightly warmer house, rear hatch open, warmer skimmer), I might be able to pull off a kalk-based system.
I'd recommend starting with kalk, as with any tank, and then if you really need additional supplementation you can step it up to 2 part. I've thought about calcium reactors, but I don't have the space, or a sump, and I imagine the nano reactors aren't that good (as with most other nano equipment, except this Aquamaxx skimmer that skims the scales off my fishes).