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Is this going to be primarily a track bike you'll occasionally ride on the street, or vise versa?
Are you the type who wouldn't mind "downgrading" to a 300 or a 650 on the street?
Realistically, your 08 CBR600 is worth $4000 max now. You could get a $3-4000 SV650 that's set up well for track, but it'll be tough to find one with street bits on it. For a bike to not be paranoid about crashing, it's probably not going to be pretty - if you don't mind riding a beater on the street, that's one thing.