At your weight, and if most of your kiting is here (where winds are rarely over the low 20's), I'd look for something in the 135-142 long by 40-43 wide. For your price point, you are probably looking at getting a used board. I'd look for something 2007 or newer, as most of the manufacturers had gone over to snowboard-type construction by then. Have a look here:
http://www.ikitesurf.com/classifieds.iws?db=kiteboards sort it by date listed to see the newer postings first. There are 800+ boards there. Post back with questions on specific boards that you think might work. There's a good chance that someone here would have the same board or know something about it and can give you some feedback. If you find one you think might work, don't be afraid to offer less than they are asking, especially if there are no previous replies shown in the ad. Second hand gear isn't selling too briskly these days.