Columbia Gas Disaster / New Boiler questions

Hi, My house was impacted by the Columbia Gas disaster in Massachusetts and will require a new gas boiler. Columbia Gas will pay to replace condemned appliances with like-for-like appliances, but I don't mind covering the overage if it gets me a more reliable boiler. I have several questions I was hoping this forum could assist me with. Home specs:

• 1922 Colonial (picture below)
• 2,200 square feet, 4 bed, 2 bath
• Windows: Anderson 400 Series Woodwright® Insert Windows
• Insulation: some loose wool insulation in the attic (10" floor joists); no insulation in the walls (I'm in the process of scheduling an insulation company blow insulation into my walls / replace attic insulation, but they require a working boiler first to perform a combustion test); my house has a lot of air leakage
• Family: 2 adults, 3 kids

Image may be NSFW.
Clik here to view. Current Appliances specs:

• Boiler: HTP (f.k.a Munchkin) MC120 Gas-Fired Circulating Heater (needs replacing)
• Hot Water: HTP - SuperStor Ultra Indirect Water Heater 45 gallons (not being replaced)
• HVAC / Air Handler: Hydronic / High Velocity; Unico System, Series M; (Heating Module: MH3660; Blower Module: MB4260H); located in attic (not being replaced)

Image may be NSFW.
Clik here to view. Questions:

• I was told by a HVAC / Plumbing company that Lochinvar Boilers were the "Cadillac" of boilers and extremely reliable - is this true? Are there other boilers that fit this description (money not really an issue assuming it's priced somewhat comparable to the Munchkin MC120)
• What make / model / size would you recommend; would this recommendation change if I insulate my walls with Class I Cellulose, replace current attic insulation with a 10" layer of R-37 Class I Cellulose (can't do more as we require the attic for storage), and air seal vs. do nothing?
• Any recommendations for reputable companies / named installers or how to find one (would asking the manufacturer be a place to start)?
• Is blown Class I Cellulose the best option for a 10" layer of insulation in the attic? I have a slate roof and no vents.

Please note my current boiler is wall mounted, but I'm open to changing if there is a better option, as long as it doesn't require changing my current system as a whole.