In the process adding on to our house and increasing the square footage from 1400 to 2800 sq ft. We will end up with 2 full baths (with tubs) in the new space and all plumbing will be in new addtion. Family of 6, with 3 girls under 10. DW likes to take baths 1-3 times a week.

Currently have a gas fired 50 gallon heater that is 12 years old. Venting is in chimney (house is 1955). Was planning on replacing with 75 gallon, but model estimate from plumber is $2400 to change to 75 gallon Bradford White (M2-TW75T6BN), which seems expensive, considering I paid $400 to put the 50 gallon in 12 years ago. Some of that cost is due to installation and moving the hot water heater to a new location.

Several plumbers have come by and looked at the total job and no one has recommended a tankless solution. Reading GW, I see many have used two 40gal or two 50gal heaters in tandem or series. I'm looking for some advice - should I consider tankless, perhaps with a buffer tank? Is this price of $2400 to install 75 gal heater high? Should I go with two smaller (standard 40 or 50) tanks?

We are doing a new furnace as part of remodel. Current furnace is vented through chimney near hot water heater, but will be moved to a new location. I'm not well versed on venting, but am concerned about a the noise of a powervented hot water heater....