The RC DOES NOT have a worse power to weight ratio than a 600.
hahaha yeah, but it does. in stock form anyway
rc51 is 133 hp and 489 lbs = 3.68lbs/hp
600rr is 118 hp and 420 lbs = 3.56lbs/hp
but who really cares? the 51 sheds 30-40lbs pretty quickly, so it doesn't matter really. the 51 is far from fast, but it doesn't pretend to be, it hasn't stopped it from reaching essentially legend status. it's just funny how many owners are in complete denial about its spec.
OP, my bike previous to my rc51 was an orange 08 600rr (pretty well the same as yours, but with more parts). the only thing i miss about it is the weight and handling. the rc51 is a great handling bike, but the 600rr is a goddamn scalpel. they are NOT the same.
obviously i made the same change, so i would definitely recommend you do the same. the rc51 is a really awesome bike, it's fun to ride, fun to own, and sounds amazing. just make sure you don't buy a ratbagged shitty one, as it seems that the market is saturated with them. too many clowns ruining these bikes so good ones are hard to come by, but i promise you, you'll regret buying a messy one with aftermarket bodywork. if the body isn't clean and oem, don't buy it.