Kinda hard to understand that last post of yurs there... but I'll try my best to respond.
Well kinda sounds like you really want to learn to playboat. As long as you feel competent on grade three, then your fine with a playboat on it. But lemme put it this way.. remember the first or second time you paddled a grade three, you got tossed around, nearly rolled, and were nervous?? well for the first few runs the playboat will feel like that. You definately get tossed about. So: If you pick a boat for river running so you can run grade threes there is a chance for you to get bored as you progress your river-running skills. The small playboat will definately keep you interested. I was on some Class II-III today in my project and it's more fun than I had ever had in my 4Fun.
You could always hold out for a boat like the wavesport FUSE, which is a true playboat/river-runner cross... and There's a bunch of boats that can run rivers and play well. So.. I would DEMO DEMO DEMO and DEMO again until you find a boat that will fit your style and make your soul sing.