Obviously you'll start with your head unit and speakers for the front doors then there'll be the sub and amp and the wiring which should include :- a fused live wire, a good set of R.C.A.'s, a remote on wire (to switch the amp on with the head unit), a earth cable and enough good oxygen free cable to connect the amp to the sub. I would advice you to get the best quality and thickest cables you can afford.
Fitting:- When you fit the system you may wish to first fit sound proofing, when you connect the live wire to the battery have the fuse as close to the battery as you can and I would run the live across the bulkhead and down the driver's side of the car (same side as the fuel pump) this will allow you to run the R.C.A cables and remote on down the passengers side of the car reducing the chances of interference from electrical systems. As for the earth cable there are many different schools of thought but I've allways used the shortest earth cable I can making sure that its secured to the bare metal of the car. As for the front speakers it seems as though the most used locations are the door pockets (obviously) for the mids and the dash recesses for the tweeters.
I've probably left out or forgot a fair bit but I think these are some of the more important aspects of fitting, the last thing you do fit should be the fuses as I would remove them from the live wire and the amp until the installation is complete and ready to go.
As far as cost goes your best bet is to look around and see what you like the look of, try and read reviews on products if you can. I have a 12 inch Vibe ported enclosure and while not producing insane bass it is more than enough for my needs and easily enough for a hatchback the size of a Golf. Try and get a sub and amp that are well matched and it mite be cheaper to get a mono amp that is purely for running a sub, if you buy a fairly high powered head unit you may be happy just to use that to run the front speakers and get a amp for them at a later date if you felt it needed it. I have an Alpine head unit that has a sub pre out which is nice because it allows you to independently control the sub volume and frequency so if you want more or less bass you can get it without having to turn the speakers up or down by the same amount as the sub. My front speakers are Vibe SA - K series and there very good and I run them with the head unit and they sound fine.
Have a look hereÂÂÂ
http://www.vibeaudio.co.uk/As I said I'm pretty sure theres loads I've left out so if anyone wants to add to it greatÂÂÂ
