I have yet to try a known cultivar, mine are twigs.
I have heard many call sunflower pretty underwhelming, if i was going to do a single tree i would probably go another commonly recommended variety and once 4-5 feet tall look at grafting a pollenizer branch or 3. I think if you had allegheny, Shenandoah, halvin, overleese, etc. in some combination you would be well-set (only reason i didnt put mango in there is i am uncertain if its vigor might be a problem in a multi-graft)