Yeah, I'd say 600 is a bit steep for a goal right out of the gate. You should gain a bit, and see how you feel about having a little pudge before you decide to go for scale-shattering.
I'd say that if you're basing your decision on whether or not to almost quintuple your weight on the comments of people on a fetish site, you need to seek urgent psychiatric help.
Gain if you want to, by all means. But make it because you want to, not because we want you to.
