I need some info on how much my car is worth

i wanna sell it...i have a cavalier gls 16v, it has alloys, tinted windows, double exhaust, big airfilter (don't know what it's called) cd/mp3 player, custom window wiper and indicator levers, m reg 2ltr 6 months tax, 7 month mot, runs like a dream but to big for me, not sure how much to ask for it tho