The Perception Pescador 12 has a weight limit of 350 and it's a great kayak. They're about $550.00 at Academy. I've paddled one for a couple of years and found it to be plenty stable.

You don't need 500lb capacity that's 200lb of gear. I am 6' 1" and 275. I bought the Field and Stream Eagle Talon for under 400 bucks at dicks sporting goods several years ago and have been very happy with it. The only drawback I have found with it is the stock seat sucks. 50 bucks for a better, higher back seat and I've been very happy. Yes there are better yaks out there but in my opinion it is the best SOT fishing kayak under 600 bucks.