Can't answer your carpc questions as I don't have experience with those items.
Decent choice of front speakersi realise this is a car pc forum, but you know, while I'm here, is that setup any good? Kinda mixed the brands up a bit there, but I'm open to advice...3
Sub - not something i'd buy
Skipping the rear speakers - good decision
Without a budget I can't accurately recomend an amp or sub package.