To ROYP.
I pick up replacement 100AH batteries  from  the local  battery supplier for a fraction of the original cost. They replace them from computer back ups  after nine months so they are almost new. The Amish are starting  to pick them up to run with solar panels so the have electric  without being hooked up   to the outside world. This  makes it a little harder to get  the batteries. 
300AH is nice  but I physical pick them up and us them in my boat  for the electric trolling  motor.  !00 AH weighs  about 60 pounds. 
How  heavy is a 300ah?