I’m kind of in the same boat, as I have a Custom Auto Sound USA-230 200W x 4, so I ordered the $50 4x10 Non A/C dual voice coil dash speaker from WCCC, and added some Kenwood 150 watt 6x9 speakers to the rear pkg tray of my 67 as to keep it as stock looking as possible. I also ran new speaker wires as well, but the system sounds terrible, and the front dash speaker is a modern dual channel speaker that actually sounds worse than the original factory. It seems that I need an amp, but I’m worried that doing that would overload the original power system / alternator, as I have all original wiring that feeds the stereo. Hoping to get someones advise on this. Thanks