My 10 year old car needs a new stereo system. It currently has just the head unit and 2 pairs of 6.5" speakers. I plan to replace the head unit with a more powerful one and replace the existing speakers with better 6.5s. The system thumps but doesn't have enough mid-range, and the mid-range it has doesn't bring out the guitar crunch like I want. Recommendations on head unit wattage and speakers that produce a good metal sound are appreciated.