if you want to be able to resell the sytem when you go turbo then buy a bolt on sytem thats good quality and stainless, like the SP full system. once you go turbo you will need to get a larger exhaust system to increase the flow say 2.5\" where as with a NA car you want to keep it around 2.25\" so the car will have some back pressure (assuming you have a 1.8L) once you have a turbo.. it creates enough back pressure in itself for the motor and well the less restriction after the turbo the easier it is for it to spool up ( just dont go too far)
so basicaly... you have to options... save hard and live with what you have till you have the dollars for the full turbo setup.
buy a good stainless bolt on system such as the SP and alike from mania and once you go turbo, sell that and buy a system suited to a turbo.
oh.. sorry you have on other option. buy cat back system for a turbo and live it till you get the turbo
i'd go option 1 or 2 though...
1 being cheaper
2 being fun..er