Beginner bike: '08-'10 Ninja 250R or 650R?

[Matrix]

I am a beginner rider and am looking to purchase one of the two posted above. From what I've been reading the 250R is pretty much the best beginner bike on the market, but I've also read that shortly after I get the hang of it I will want something more powerful. So, my question is, is the 650R still a good beginner bike? It's not TOO powerful, it'll run circles around the 250R, but a 1000cc will blow it away. So I'm looking for a beginner bike, but not a little bike. I also don't want to kill myself...so if you EXPERIENCED riders could please give me some advice I would really appreciate it. One of my buddies rides a Yamaha r1 1000cc and thinks the 250 is too small for me and the 650 is too big for me. (power wise) So once again, advice is very appreciated. Thank you. BTW: I am 6'0" and 175lbs. 17 years old. Thank you.