I'd throw the 400EX and the Z400 into the mix. You'll see better performance than the Yammi 350, and good low end torque so you're not shifting all the time like with the 450's... You won't keep up with the 450's but you can stay close. And the 400's ride is very nice. My experince with the 400EX is that they're bulletproof. I've only had to perform regular maintenence, and never had anything break.

My 2 cents.