kawasaki for a 600, and the yamaha R1 if a 600 isnt rediculus enough for you. thats my personal prefference.

i want a kawi 636 and ive read from a lot of different places that no 600 bike can hang with it, and "it makes a certain 750 very nervous".

but i will agree with ewood, about 95% of the people who buy a 600 sportbike will not be able to fullly use the proformence a 600 can offer, much less a liter bike. it's all personal preference as far as look of the bike goes, and how comfy you feel on the bike. all the 600 sportbikes look the same to me, and the 1ks are getting more and more alike.