you still haven't really narrowed down exactly what you want to do. You say you want to be able to do rodeo tricks, but want a 7'6" boat? Again thats 2 different boats. I have a jackson 4fun river runner/play boat and its 6'4" (quite long because I am tall) but your average boat is going to be under 6'. It runs quite well, fast enough and can surf and in theory do trick though I have not good enough yet. If you are just getting into it I would suggest using http://www.americanwhitewater.org/content/Affiliate_view_
to find some local groups or shops. They often have demo and class nights that let you try out various boats and get some tips on what your looking for based on the paddling in your area. Most groups also have classified sections as paddlers are gear whores and constantly sell their older boats. Also if you are fresh into it take some proper lessons, it will speed up the learning process, be way less frustrating and make you safer/quicker. We regularly paddle with beginners and you can tell who has taken lessons and who hasn't. Do it for your sake as well as everyone elses.