I am trying to decide what type of heater source for my hydronic radiant system. I believe I have a few choices:

1. boiler + indirect tank for radiant system, with separate water heater for domestic hot water

2. high efficiency and powerful water heater like a polaris, or bock, for both domestic hot water and radiant system (through a wall mounted heat exchanger).

3. tankless water heater for radiant system, and regular tank heater for domestic hot water.

4. two separate tanked water heaters, one for domestic and one for radiant

Am I missing any choices? I like #2 the best since it's the simplest and probably the most cost effective (after including all labor). However, I am worry the polaris 50 gallon will not be strong enough to provide a radiant system of 4000 sq ft. It will be separate in 4 zones, 2 1000 ft zones, 1 14000 ft zone, and 1 600 ft zone. In addition domestic hot water needs is for 2 adults with 2 kids with a bathtub in master bedroom, and I can imagine having 2-3 showers running simultaneously. Does a radiant system normally cycles on and off alot? Meaning do I have to worry that I can't have both domestic and radiant drawing water at the same time?

Lastly, instead of a wall mount heat exchanger, can I connect an indirect tank (which has a build in heat exchanger) to the polaris? If so, is the extra tank capacity be useful for storing some heated water? What I read is that the indirect is fed from the boiler, and I wonder if it can be fed from the Polaris instead. Also want to see if the tank can be helpful in minimizing heat loss and increase storage compare to a wall mounted heat exchanger. I would imagine a simple wall mounted heat exchanger will lose heat to the surrounding, and even if it's insulated it must not be as insulated compare to an indirect tank.