intake is a nice mod......if you dont really want much from the car in the way of power i suggest just getting a new muffler, not entire catback. and as for low end, get some iridium spark plugs and plug wires
also, an AEM intake wouldnt hurt.
header/catback will usually be more for top end than low end......so i dont suggest them since quite often they lessen your low end.
which is why i said just an aftermarket muffler like from Ractive
or APEXi or something. whatever you like.