Agree with William. The concept behind dual subs is to even the response throughout the space. Mixing different subs defeats that purpose as the response won't be identical. Sealed units having a quicker response is a fallacy. Ported units work just as well in the mid band and will perform better at the lower frequencies. It's generally accepted that ported is better and that sealed units are more for situations where space is limited and size is the major concern.\n\nPB2000Pros would be plenty. PB3000s would be killer. Ultra16s overkill. :D Bear in mind how big the boxes are. The 3000 has a 13" driver and the Ultra16 a 16" driver. They are big boxes. The 2000 and 3000 are black boxes with rounded corners and rather plain and unobtrusive. The Ultra16 is more of a statement piece that will catch people's attention. If you want a sub that also has a lot of visual appeal like the Ultra16, you should also look at the Arendal 1723 2V.