Adam, please take anything from me with a huge grain of salt. I'm probably one of the least experienced folks on this forum, having just started riding bikes on the track last year with N2. I'm 6'2",about 215, and am long waisted. I've been riding bikes for more than 40 yrs both on and off road (motocross, hare scramble, etc). I got suckered into this addition by an obviously brain damaged friend (Mannix) and his evil sidekick (Musky). I started with the R6 because another friend gave me the bike to use so I wouldn't destroy one of my street bikes. Free is good.
I'm really glad I started with the R6. It's an awesome bike, and is obviously capable to be far faster than I can ride it. But, it's an '05 and the riding position with the tail section coming straight up behind the seat forces me to be really tight on the bike. Plus, at 215 without my gear, I am constantly wringing that R6 motor for all it's worth - ESPECIALLY with the new elevation changes at places like PittRace full. I had the opportunity to ride my brain damaged friends GSXR750 for a session on Sunday, and I found it far easier to move around on the bike, and my braking was even more effective for corner entry because I didn't feel so forced "forward" under heavy braking. The torque curve on the 750 made gear selection easier, and I could concentrate more on body position, etc and less about making sure I was ALWAYS between 10000-14000rpm. I think if I weighed 40lbs less, and was a few inches shorter, I would absolutely stick with the R6. As for too much power right off the bat, I'm the wrong person to ask.
My advice is to find a couple other "friends" at the next event you're going to and take a couple laps to see where you're comfortable. Better yet, find one of the CRs that really have great body position, and have them take a look at you on a couple bikes with you getting off the bike and in a tuck. See how it feels. One thing I know for sure - 99% of everything on the track ain't the bike.
BTW, while I will maintain to the death that my friends are brain damaged and evil, they're good guys and I owe them for helping me to stay alive on the track and learn a little bit