pair of aura30/50 combos. they are sold at meci.com. dont be fooled by the cheesy site layout, they are alright people to deal with. i didnt get a chance to listen to an aura50, but my aura30 was much better than acs48, i tell you that much.. it was even comparable to my midiland s2 4100 except a bit less power (but hey you are paying only $100+shipping for a dualsub quad setup )