trimxer: how much have you played around with your current setup? My 01 wouldnt do anything good and i thought i had big problems since it had been revalved by the previuos owner but i didnt know what he looked like eg, weight riding style etc. After a while, i found that it wouldnt turn because of the wrong sag, felt stiff because too much rebound making it pack etc. etc.! But just playing with the cliuckers has made it work sooo much better. I expect even a custom revalve will have some setting up required. However, there is also the confidence thing, and i will eventually get a custom revalve to help there and get me in a good ball park for my parameters (the other owner could have been a pro SX rider or a slow dufus, since i have nothing to comapre with).
IMHO, Stick with the YZ, it has a great reputation as stock, ive called several suspension companies about my problems and they all say the 01 is better to work with than the 02! Ive had mine ported and it has an awesome motor, i am trying to find someone at the track with an 02 for a back to back test!
mxc400, i may get corrected on this, but you may get away with the bigger springs and stock valving if you can turn in enough rebound to cope with that spring, its probably worth a try.