the 125 is nice for learning, but if you really wanna get hurt, a 250cc+ motor will get the job done. i have a montesa 314r, i'd like to get a 315, but the 314r works well enough.....but then again i suck at trials. i'm 5'11" and 180...sorry i got no recommendations as to gg trials. never owned one..
this looks like a decent deal and in your neck of the woods... hard to find any modern trials bikes for much less...
http://www.advrider.com/forums/showthread.php?t=511117