That's ok, we have to start from somewhere. I think the biggest thing i learned was about speaker sensitivity. Anything below 91 dB @ 1 watt/1meter is pathetic outside of home theater or spoken voice use.
But what does the 1 watt/1 meter thing mean? It's a general standard, you feed a speaker or speaker system exactly 1 watt (Also something like 2.83 volts RMS) and measure the output from 1 meter away. The reason this matters is that amplifier power doesn't have a linear effect on speaker output, going to 100 watts from 10 isn't going net you a system that is now ten times louder. Actually, once you begin to exceed a speaker's rated sensitivity you need double the power for each additional 3dB, up to the speaker's maximum SPL limits that is. So to take a speaker rated at 91 dB @ 1 watt, you need 2 watts for 94 dB, 4w for 97dB, 8w for 100dB, 16w for 103dB, 32w for 106dB and so on. For reference, a typical rock concert can be anywhere from 115-125dB and hearing loss can happen rather quickly at 115dB and beyond.
But back to stock radio systems, you can see why high base sensitivity numbers are important, as we only have about 10 watts to work with and it doesn't take us very far. Outside of the car, sensitivity is critical to SPL junkies like myself who want to be able to produce peaks of 120dB or so and who are running multiple amplifiers. If it wasn't for my current system's rating of 101dB, I'd have needed to upgrade my electrical service and spend bigger bucks on amplifiers capable of 300 watts or more, double that for the subwoofers.
The second most important thing is about amplifier power rating. Don't even bother with peak output, focus only on RMS output and generally the 8ohm rating as that's what most speakers are rated for (home use). The better an amp is, the more likely it will be to "double-down" it's RMS power rating going from 8 ohm to 4 ohm. If an amp doesn't have a 4 ohm rating, it most likely isn't capable of driving a load that low.
Slew rate rated from 20hz to 20khz is a good one too. Anything above 10V/us is good. Most amps rate above this nowadays since they skew results by testing above 20khz. No point doing even above 16khz unless they're trying to sell radio equipment to dogs.