I just upgraded my system to the 10" burner. But really, any of the ones you listed will work fine. There is a place just down the road, in Lumberton, that stocks those same burners. Agri Supply. The stands may be a little different.
is there a minimum BTU's that I need for 5 gallon batches?
No there isn't a standard number. Get the SQ-14. It puts out 55,000 BTU's and has a big enough frame do you'll be able to upgrade to a larger pot eventually. We've done testing and the SQ-14 can get 10 gallons of water boiling in ~40mins.