Need advice on Boiler selection

Home heating system replacement--any advice on selection would be appreciated

I am looking for advice on replacing a failing heating system in residential home in Southern NH. Here are the details:
30 year old oil fired boiler with tankless coil for DHW.
115,000 btu
appx 3000 sqft--and tight
consumes only about 600 gallons of oil a year
The distribution system is forced hot water base board (about 210 linear feet of finned), 4 zones that will not be replaced.

I am trying to decide:
1 Does it make sense to switch to propane
--cost effective due to the added cost of need for chimney liner?
--lower maintenance costs
--Higher efficiencies (offset by lower btu output
2 direct vent condensing boiler--there is no low temp demand such as radient flooring
3 which brand would be best suited/best bang for the buck
--Buderus and Viessman have good reputation and higher claimed AFEU, but are they worth the premium price
I would also like to add outdoor reset controls and an indirect HW tank.

Looking for a cost effective solution, mainly between oil and Propane, and between brands/models. which ones have better realized efficiencies, less service issues, cost effectiveness, etc.
I welcome all advice from experienced professionals

The first thing is, without a good manual-j heat load analysis, you're shooting in the dark. Going by the info you gave is not enough to get a WAG. Now, you can get a WAG, or better than that, by using the oil used/verses heating degree-day info, but it is only an approximation (usually, upper bound). A condensing boiler may or may not be a good choice. You have a misconception about the low temps...with an outdoor reset and a properly sized and installed condensing boiler, you only need higher temps on a really cold day, and the thing is likely to be able to condense a good portion of the time. The hassle is with four zones, if only one is calling for heat, your heat load is likely to be below the minimum of even a modulating boiler which affects any boiler's efficiency. Adding an indirect WH as a zone does NOT constitute a good reason to make a boiler larger. Size it properly, too for the anticipated load, and you should never run out of hot water or notice any degradation of comfort in the house.