I have the bk 800.4, the bk 1800.1, and the bk 580.5 all running active.... My front stage cost less than 200$ for vifa tweeters, silver flute 5.5" midrange and 8" door mid bass and it gets LOUD... All running 4 ohm on stock electrical (besides big 3) with ab amps for the highs and the 1800 d...