for an example look at my setup in my signature. That came to a total of like 900 bucks minus the head unit.
now u can do things differently like u could get 1 12" D2 and get a 1000 watt amp which would be cheaper than my sub/amp setup price or around the same. as for speakers i definetly recomennd taking out the rear fill, get one nice set of components up front, mine costed 150, and theyr soooo great for the money.
for ur questions abotu audiobahn, theyr subs sound like PooPoo. and MB quart speakers come with HARSH tweeters.