So I have been brewing for a few months now, and I am always looking at how to make my beer better. I decided that I wanted to do full boils and start AG soon. Although I have had trouble boiling 3-4 gallons in my 20qt SS pot.
Spreading that over 2 burners helped a ton. I could get a strong rolling boil of 4+ gallons.
I just bought a 30qt aluminum pot to do deathbrewers stove top AG, and I thought that I would have to do a split pot boil.
I was boiling up some water to get the oxide layer, and it turns out that if I put the pot on one big burner and a back small burner I can boil as much as the pot can hold.
I live in a studio aparment, and its just your standard electric stove/oven, and I can boil 7+ gallons.
Moral of the story try putting your pot over 2 burners, and don't make assumptions about how much your stove can handle until you actually try boiling more.