wbwood - it was a wrong number. Some $10/hour guy in sales support, he doesn't know sh-t about his products and probably no college education. "Voiding the warranty" is a very common BS in this industry though.
You've got answers from several people here that you can and should use a bigger controller if you use a bigger solar array. 20A, in this case. Buy a good one (this advice was also repeated by several people).