new boiler

Andy_17

just finishing a renovation on a 3000 sq' home& need a larger direct vent,natural gas boiler. 1 st. fl full radiant heat w/ hot water coil on air handler for back up.
2 nd fl.heated w/ hot water coils in air handler & radiant in bathrooms. I would like to use a indirect hot water system to run 2 1/2 baths,6 people in home, 1- 50 gal. whirlpool
1- how big of a hot water tank should I use?With the prority relays in use, is there a major affect on the heating output or does it not run long enough to be noticed?
2- Can I use a condensing boiler w/ the temps. need for the hot water coils?
3- since the radiant & forced air run @ such different temps,do I need to use a triple bipass boiler?

I have learned a great deal from this board & have a new found respect for all the heating guys out there, I never realized how much knowlege goes into a good heating system.
Thanks