One guy mentioned a Kinetic, and this recirculates an old debate.
Kinetics and older boats like it don't have the flat bottoms of today's boats.
I learned in a Kinetic - and it was awesome at first. Really stable, tremendously fast and easy to roll. I could punch any wave and almost any hole in that boat.
If river running and confidence are most important to you, A Kinetic would work and I would sell you mine REALLY cheap. Maybe $150.
The reason I would sell it so cheap is this: If you are aggressive and think you might want to play, i.e. learn to cartwheel, surf waves, etc., the Kinetic will hold you back drastically. You may only want to paddle it for a month or two or six, and then you'll want a new play boat. But for $150, maybe that's the way to go.
Give me a ring if you'd like to try the boat.