When I upgraded, I wanted the same thing.  So ended up with a 6 ply tread and went ahead with new Alum wheels to help keep unsprung weight down. Forget the brand, but it's tread pattern is an angled series of bars like a UTV tire, works great.  Had em add in slime and mount the wheels, was just over $600.  On on-line speciality place, are several to choose from.  I can check the brand/model if you like.