I'm an avid paddler as well. I was big into whitewater until I almost drowned and ended up in the hospital. Long story.
Read Lone Wolf's post above. Then re read it. Study it. He's telling you a whole lot of wisdom in a small space. The only thing I can add is that I have an Old Towne Loon 138 now, and I love it. The Loon 138 is the right size boat, with the right characteristics for what I do and how I do it.
The most important thing is to to actually paddle a boat before you buy it. Everybody's different, and so is every boat.
Also, don't forget the paddle. Never forget that your paddle is your motor - don't go cheap. A few hours with a cheap paddle will kill your arms. I use a Bending Branches paddle and give them 5 stars.