If I had 20k in one lump sum to put into a ski, I'd come to my senses and put it into my mortgage instead of a hole in the water.
But, since we're spending your money here....try out a variety of boats at flatwater Friday and see what hull you like. Most of them will flip easily with the right motor. Go for a carbon hull that suits your riding style. A Freak would be an excellent choice, as would a BOB or a Rickter XFS/XFR. Spend the rest on a mag pump and a motor as big as you can afford while still leaving money for the necessary accessories for that motor (big carbs, total loss, race gas)
Unless you're buying used, 20k won't get you an exceptional flatwater setup. Half of that is likely to go to the hull unless you buy a BOB.