Find a good deck. Kenwood excelon, pioneer premier, alpine. Something with usb input and aux headphone input. 6 channel pre outs around 3-5 volt. Possibly even sat bluetooth and hd radio ready if you want. For speakers id do components up front. With a little modification to the stock brackets I was able to fit 6" boston acoustics and im still able to put the stock speakers back in. I glued the tweeters to the stock location. And there was plenty of space on the door for the crossovers. For the rear a good set or 2 or 3 way 6x9s will do. I used 6.5 components in the rear with adapter plates. Only because I already had them. Amp for interiors should at least be 100a watts max per channel. Works well for me. For bass its all about preference. Fast tight bass you go with 10s for deep long lows 12s or 15s work. And a good power and ground setup. I've been pushing it using 4 gauge wire for 2400 watts in my last 2year cars and its been fine. I should upgrade to a 0. As for cost I've spent around 800 over the past 4 years. Some free stuff some used and some new. Ebay and craigslist are your friends. I've saved around a grand using craigslist and ebay. Shop around. I saved 100 on my deck brand new using ebay over crutchfield. Sonic electronix is a great site too.
