need audio suggestion, 4 channel amp, 1/2 channel amp, and sub

[Fenvy]

hello, I don't know what to buy so I am goign to ask you guys

the 4 speakersI have an alpine deck and some alpine speaker all around... the deck output 50w max per channel, I am guessing the rms woudl be less than 20w. The speaker rated at 25wat rpm and 125max... does that mean I can get a 4 channel amp that's rated at 50w rms to increase sound quality? any recommendation on the 4 channel amp?

subI want to get a 10" sub, box and either mono channel or bridge-able 2 channel amp... any recomendation on the brand of sub and brand of amp? I don't want it to be a load to my alternator or the battery, I need a capacitator then? what is a good brand?