if you want to have a full range of sound in your car then you need a sub, saying a sub is chav is like saying anyone with a 5.1 cinema setup is a chav
having the sub ramped right up, windows down playing cd's from the front of max power is chav though, whilst in halfords car park is 110% chav though.
Personally i'd say 2 * 8" subs on a stealth shelf is enough to add the missing dimension to the sound, but then it depends on your music taste really.