hi i have a 58 plate series 2 grande punto and was wondering if i could connect the standard head unit that the car comes with to a sub and amp?

Yeah it has been covered in quite a bit on this forum look for RCA converter
, line level converter etc you should be able to find what you want. I you have any further questions dont hesitan
te to ask.

just mentioned this on another thread, but look into Alpine pxe h650, rockford Fosgate 3sixty.1, or jl cleansweep, step up from pure rca convertors, but offer a lot more.