600cc liquid's are far from beginner sleds. As someone else mentioned, they will kill you just as fast, if not faster, than an 800. (lighter, so you might decide to jump a little more, and that doesn't always end well!)
First of all What kind of riding do you intend to do?
IMO If you're new to the sport, riding a modern 600cc sled trying to keep up with more experienced riders could be a recipe for disaster. Not trying to knock the opinions of others, but it seems most folks here are performance enthusiasts and to them a 600 is a middle of the pack sled.
FWIW I'm a 49 year old man who's most enjoyable sledding experience ever was the first time I rode with my 12 year old daughter on her first sled, a 440Z Cat. Different strokes for different folks.
2004 MXZ 500SS
2003 Pantera 550
1988 Springbok Bowrider/110 Johnson