Exactly Der Jaeger, .577's and .600's were only ever used as back up by pro ivory hunters, they never carried them themselves and rarely used them (good shots with the lighter stuff). When the ivory "business" dried up nearly all normal pros, guides etc went the .470/.500 route even the cullers. I see no reason to buy a .577 or .600 unless you WANT to own one, you will never need it in todays world. Doesn't mean you shouldn't want one though but I think a .500 is a better choice,
just my 5 centimos worth

best, Mike