I still shoot a Q2 as my main bow ( for the last 6 or 7 years) and have looked into it's value a few times. I would say with a $50 sight and a $20 stabilizer (kinda cheap accesories) it might be worth around $400 max.

Make sure how old the strings are because if they need changed, you may pay another $70 for that. I can't remember how much it cost me last time but it was somewhere around that.