Under Seat Sub With Standard Headunit

[glenn_adam_doble]

i've had a search, it has been covered many times but i still dont quite get it, as car audio is something i have never really fiddled with before.

i am after a small under seat sub something that will never get seen, i couldn't live with a boot one as they look so "chavy" and never really look right unless you go nuts with fiberglass.

i dont want a big kick just a little bit more "ummphh" on the bass,

i want to use the standard head unit as it has all the bluetooth and ipod connectivity and my carminat tomtom and works with the remote stalk.

i realise in a ideal world a headunit upgraded would be better but for a similar spec'd headunit in terms of functions would be dear or look ridiculous.

so what do i need ?

do i need an amp ? suggestions?

also suggestions on subs ?

anything else Wiring etc.

looking at around £125-

Thanks Glenn