go to halfords, ripspeed and get a package deal, they have all the wiring etc, or just get the part numbers and buy the bits on fleabay,
i had a nice system in my 110, with a little sensible driving and minimal sound proofing (a few carpets) i could hear fine, would suggest specific items, but i went with a budget for each item and bought what i could afford. only spent 20 on 2 speakers and 80 on head unit. all sony.
it can be done and you will hear it! unless you have no soundproofing.