MB Quarts are still available but I wasn't exactly pleased with their sound last I audiotioned them. I actually liked the Boston Accoustics better and the JL sounded comparable though both are much less. You can actually get MB Quarts way up there in price to with their Q series (around a grand for a set of components).
Obviously there are cheaper options out there that will still sound good than what I quoted. That also included about $1600 worth of install which may or may not be important to you. Boston Accoustics are a good place to look to minimize cost and you could do the install yourself if you wanted. The tricky part is getting the sub to look like a part of the car which you may not care about at all.
