Need some Mach 460 advice

Sorry if this is a little long. When I got my car it had the Mach 460 system, but the previous owner installed a new head unit, removed the whole rear rack, put the stock woofers back in the rear and remounted the amps to the back of the rear searts. The rear tweeters are no longer there. The rear speakers were blown and sounding like crap, so I replaced those with some 6x8s. The 6x8s though are only receiving the highs. My questions is, if I was able to get my hands on a whole rear deck system, amps, speakers included, should I just try to replace everything with the stock stuff? Or should I take out all the Mach stuff and put some components up front and leave the 6x8s in the rear? I'm not looking for thumping bass, just enough bass I can notice and a nice clean sound. Any advice would be appreciated.
 
If you can get the entire rear tray asembly,then you should be able to get the wiring harness attached with it. It runs about 18 inches up the rear driver's side wheelwell. If the factory harness is still there,then you should be able to just plug it in and go!!