Hi ya chuey, for the box size, if you have space for more then 4.5 cubes per that would nice. You can always shrink the box by adding wood, much easier then trying to increase the box. As for power, IKESound has some of the '06 model Merlins cheap and an MD3 for the MJ's would be a very clean pairing. I really like the MJ personally, and love it sealed, but need to try it ported. But for of them with good clean power will be unreal. As for the pricing on the Mach5 subs on the shop now, Mark did some module correction and the shipping is not part of the initial price is now added on, so your end price will be lower now.