This is kind of a complex deal, but I think it would get you the boat you are looking for. Be patient, here's the story: I paddled a pyranha S8 as a beginner and am 5' 10" (was) 180 lbs. It was an unforgiving boat to learn in, but fun as hell and ultimately made me a better boater. The S8 is slicey, and easy to learn to cartwheel. The stern volume is low, so you learn to lean forward through rapids, and incidentally how to stern stall mid-rapid. It surfs really well, regardless of whether you are interested in surfing it.
So here's the deal. My old S8 lives in Boulder with a dear old friend. Problem is that old friend is too much of a pus to learn in the S8 and wants an easy river runner (like an RPM or similar). If can get an old river runner to trade for my dear old S8, that would be win win win: S8 gets back on the water, dear old friend gets a boat he's not scared of, you get the S8 for the price of an old river runner.
S8 includes: (added values!!!) Oil canning, upside down IR backband because othewise it pinches your ass and spectra-cord frankenoutfitting.
So here's a little for-example: You're getting all this advice about how you need a $500 boat and need to get your river skills, but you're a quick learner, right?! Go get that $150 RPM, learn to roll in a lake, play in the kayak park where you can practice your roll and get the feel for moving water, get sick of the big river runner boat, trade it to my old pal who's hurtin for an easy boat, rock out that S8, shock the ladies with your skills...