If you're set on a 125 and you can afford one have a look at the 06 yz125's onwards, theyre alot less band only power than a cr and in my own experience are much easier to ride quicker if you dont have much experience with them. I found on the cr's i'd always be waiting for the band to kick in and couldnt relax as much whereas on the yz it was just snap the throttle and you're off.

Like I said earlier though I started on a yz250, bought it brand new, only other motocross bike I had ridden before that was my mates kxf250. I found it so much nicer to ride than the 125's my mates had. It flew when you wanted it too but was really controllable as well, it wasnt any of this no power then bang im going really fast like the hondas. Personally i never liked any of the cr's i rode for power delivery. Stock or modded. Had a go on a crf450 as well and that was awful. felt like riding a tank around.