CRF 450's a brilliant bike too.
is there much difference between the X and the R models? i had a day on a MX crf450 (an R maybe?) in Baja a few years back. I found i really focused, and you had to be on the ball to keep it in check, fine at the beginning of the day, but it just sappped energy towards the end. Don't think it helped trying to keep up with the guide, who was also a seasoned Baja racer