Have about $400-$500 to spend soo.... Sundown X or Z v.3, Soundqubed HDC 3 or 4, OR JL 12 W6. can you guys tell me the difference between X and Z for sundown and HDC 3 and 4? does it make a difference for the more i pay? Difference between a 12 and 15? Also what would be a good amp to power any...