I agree. Home audio's a different story, but you usually have more options too (balanced vs unbalanced, analog vs digital). Not many options in car audio for carrying signal.

For your original question Carlos:
Make your own RCA's by using 16awg speaker wire, twist it in a drill and solder your own ends on. Alternatively, you could braid 3 wires per RCA end and just use the 2 wires with the 3rd a dummy, this imitates the high end Rockford cables I mentioned earlier, but is overkill I think.

Remote turn on can be the cheapest 18awg you can find.

Size of speaker wire depends on power to speakers. Typical is 16-18awg for spks, and 12-14 awg for subs.

For power wire, that also depends on size of amps, but typically go as big as you can afford. This way you can upgrade, add an amp, and there is less voltage drop. Also do what's called "the big 3". Do a search, basically upgrades alternator power wire, engine ground and battery ground.

When buying the power wire, the higher the strand count, the more flexible and easier to work with the wire will be. That's it, more strands does not mean better, usually just more expensive. Lots of guys go with welding cable, others car audio stuff. Also, OFC means Oxygen free Copper. Look for that or 100% copper, or solid copper, something along those lines. If it says aluminized copper, you have to buy bigger wire to get the same current rating. Rule of thumb is get the next size bigger (10 awg would move up to 8 awg, 4 awg to 2 awg, etc.) This is done to cut costs since copper costs alot now.