Well, I'm at $5800 in just parts and materials including controls and zone dampers and zone controller for the forced air side. Add about $7k for air handler and heat pump with hydronic coil. I could put in a furnace and heat pump for about $7500.
What do I get?
1) Radiant heat
2) More hot water capacity for mid winter. 5.5GPM with the cold, cold inlet water temps is it in winter. That's a lot, but 2 showers at once +1 facuet and you'r short. 1 soaking tube takes all of that flow.
3) The old house "charactor" of having huge cast iron radiators back in service pumping out heat.
4) More heat for the garage, making it truely heated actively. I should be able to maintain 60-65F all winter. It's 50-55F right now, which isn't bad at all.
5) More heat in the basement
6) Our dining room won't be under condtioned all the time. In winter you have ot open all the doors and turn on all the lights to get it warm.
7) zone controls so no hot kitchen when cooking, not hot or cold dining room.
One really cool heating system.
9) during a power outage, I only need about 200 Watts to heat the downstairs, except the kitchen and provide hot water. Less if the combi will run without power to the "slave" tankless.