welcome to the site mate. lovely car. Amp and sub can be easily added to the standard headunit, but you need to buy a line level convertor which enables you to take the wiring off the woofer part of your rear speakers and you connect them to the covertor which has 2 rca plugs, which you can plug into an amp and then your sub into your amp. makes sense? Not the best setup sound wise but simple to do, convertor is available from Halfords or ebay