Don't waste your money on paying someone to make you a sub box. They aren't all that hard to make. I made my very first one out of 3/4" plywood and some carpet from the hardware store. The only difficult part is figuring out the needed airspace for the subs to work properly. But, if you're decent at math, or have internet, it shouldn't be too difficult.Hm. There's a shop that specializes in sound and tint I'll see if they can make a box for me. But you haven't done anything like where the spare tire would go or anything like that?
As for the airspace for the subs, if you get them new, it should come with an instruction page or something that tells you how much is needed for a sealed/ported box. At least that's how my Infinity's came when I got them years ago. Or, I'm sure that you could find the airspace spec online too.