A few things that I've needed to deal with in my off grid setup:

I like the MidNite solar controllers.

LiFePO4 batteries are great, with a few caveats:

  - you must use batteries from the same batch, ie you can't upgrade capacity piecemeal, to avoid degrading the new ones  
  - cable lengths are important because even small differences in resistive losses between batteries can mean that one battery is doing more charging / discharging  
  - you can't charge below 0\*C, which I'm assuming could be a problem in New England