Thanks for the reply, I guess you're right in that i'm not limited to a Sonosub, just thought it would be easier to build, but that's not really any issue. I could go cube just as easily.
I think my total budget for the sub would be around $500 max. By deep, I mean maybe around 18-20hz would be deep enough for me, I don't need anything deeper than that (or so I think). As far as how loud, not sure how to describe that, but loud enough that I could crank something like Jurassic Park, Lord of the Rings, etc and not worry about the sub bottoming out.
Another question, if I make a sub that is cube/square/rectangle, is there any reason I can't make it out of MDF and then cover the entire thing in furniture grade wood?
Are there any 15" drivers out there that are considered to be the leaders or best bang for the buck for maybe under $200? I figured maybe $200 for driver, $200 for amp and the rest to build the cabinet?