Well, as your title suggests, you could get them powder coated. Duplicolor is not a powder coat, it is just paint. Powder coating is a highly effective, very strong and long lasting (usually) process. It is not really a DIY type deal, although there are home powder coaters on the market. I have gotten quotes as low as $20 per wheel for professional powder coating. It is something to consider.
honestly, i've done my wheels in bronze, from duplicolor, and i was pleased. just make sure to have at least 3-4 cans of paint to do all four, with 3 coats. sanding sucks, but make sure u take the time to do it well, inside and out. I've pressure washed mine and there is no chipping or fading. if you got the money to powdercoat, then do so.