definitely relative, largely dependent on whether you buy new or used...
as to what you should actually get, i think, contrary to the popular wisdom here, starting small/on a tamer bike is a good idea (with the added benefit that the smaller bike will likely be dirt cheap to insure as a new rider) people get bored on 600s & liter bikes too...yea you might want more power eventually, or you might also find that the 300 (honda's got a few sporty 500cc models too) is all you need, who knows? not advising against a 600, just that a lower cc bike might be a viable option...i would definitely recommend buying used (and either bringing a knowledgeable friend/mechanic, or getting your weight up on what to look for on a used bike), whatever you decide on getting; unless you just want the peace of mind of a new bike...
good luck!