caps are useless look into the official big 3 wiring thread in the wiring and electrical section here, it is a sticky at the top of that page
the older amps are probably higher quality than the newer stuff as they used better components, but the newer stuff is smaller lighter and more efficient
no problem, after upgrading your wiring and if you still have dimming look into a better battery. Caps are probably the best marketing scheme stereo companies have ever came out with