Quite a few people drop 1 tooth on the front sprocket so for the 600 that would be a 15t sprocket (I think I have . Some also add 2 teeth to the rear sprocket and change the chain for a 520.
I have gone down 1 tooth on the front of my 750 and it has transformed the bike. Much more throttle response and pickup out of corners. If you ride twisties then this mod is a no brainer. You loose some top end, but today I got her up to 155 (140 actual as my speedo is still out):nono and I still had 3000 revs left to play with, so on a good day she will still do 155/160, which for me is plenty.
I dont feel i need to add more to the rear sprocket. The bike is perfect with just -1 on the front, also it is a really cheep mod. If you dont like it you can go back to standard and its only cost you £10 ($30?).