As to going with an high efficiency boiler or not is really entirely dependent upon your system. If your system is doing domestic hot water and you're running higher temps through the boiler (150+) you probably aren't going to see much of an efficiency boost out of a condensing boiler to justify the cost of them vs a much cheaper natural draft boiler. You really need to have condensing flue gases to see the 93%+ efficiencies out of the HE boilers.
Hydronic heating is not a cheap heating system to install that's for sure. They parts are generally expensive as are the appliances and the labour to install them can be quite intensive. But once the system is up and running and you're enjoying the lovely heat you get from a hydronic system you're going to be loving it!!!