I disagree with getting the same brands all the way through the system. You really have to find things you like and go with that. The first question is what type of music do you listen to the most. That will pretty much determine which of the sub combo's to buy. As for the placement in the tire well, you can do a lot with that using fiberglass or not to make the bottom of the box and just raise the floor a couple inches and make a false floor so that it looks like there is nothing there and you can keep all of your space. I know a lot of people dont like them but I think a JL W3 would probably perfectly matched with that amp. If you decide to go with one 12 then I would suggest the W3 with dual 2ohm VC's that way you will get a 4ohm mono to the amp. With my dealings with Soundstream you definitely dont want to go below a 4ohm load on that amp. They get very hot and have a tendency to burn up if pushed to hard.