haha ok i have to say i went to watch the MX today localy, and the higher reving 250s like the honda acctually sounded beautifulYou seem more concerned about how it sounds then anything else.
Of course you can learn on a 450f, your learning curve will just be steeper.
BTW what's wrong with 13k RPMs? My bike's always begging to go up there.
Ok I have to say, the Suzuki rm-z 250 actually sounded really nice ! Loads more low end grunt than the rest of the 250s by my judgements after the MX today, but it must have been a 2010 or 08-09 because apparently the 2011 rm-z has joined the rest of the characteristicaly high reving crew that are the 250 mxers haha tell me if I'm wrong ..!