Wirelessly, this seems to be the sort of thing you seem to be describing:
http://www.amazon.co.uk/Logitech-Wir.../dp/B000BERQCU
or
http://www.pcpro.co.uk/reviews/87368...-sla5520i.html
Personally, I have my pc hooked up to my hifi using a stereo to phono lead, with a phono extention (depending on where my pc is).
Wired will be a lot cheaper obviously, and probably better quality, but then again, if you only have an inbuilt soundcard, it wont be amazing anyway.
Hope that helps!