Dont get a snail
Try a starter 600 first and see if you can get used to the power. I got a ZZR600 for my first big bike, been on it about three month now. Had a go on a ER6 but was a bit on the slow side now i've got used to the ZZR.
Then again if you build up through the ranks you've nothing to loose. My mate has just got an R6 that is mental compared to the ZZR I like it but for me as a commuter bike just a tad too extreme and would end up with a mega neck / back ache. The sports touring bikes are a a bit detuned than the full out sports bike.
The weight difference from a 125 is good for stability but i nearly learnt the hard way when i didnt but the stand down properly and had to catch the bike, lets just say it was a bit heavier than the 125. No injuries except shame on the street me nearly being squashed by the bike