One thing I wish I did when I upgraded the stereo in my first car was look into second hand prices. Audio gear depeciates worse than an American car. Once it's been used it's only worth about 25% of retail price, so don't be afraid to check out Chashies or other second hand places (hopefully not stolen gear). The head unit isn't nessesary if you are amping the system (which you will need to do if running subs). With subs, ignore the peak watt figure as it's a meaningless figure, look for the RMS figure. You don't need to see huge watt RMS numbers to get a decent system, just keep an eye out on the impedance as an impedance difference can cause issues. I got plenty of sound of of my setup with 4x100w speakers, 1x1000w sub, 4x100w amp and a 2x200w amp. That was pretty expensive 8 years ago, now that would be pretty cheap I assume, less so if buying used.