There's a few different setups you could run for that type of system. One of the loudest systems I had in my old Grand Am was 2 12 inch MTX 5500's in a ThunderTC enclosure. Not horrible sound quality, and it hit hard. I'm just not a huge fan of MTX and wanted something else, so I traded them for the Type R.
I used to smoke in my old cars before I had a kid and got a car seat, and the Type R would make the smoke 'dance' in the car when I smoked (I guess it had the most pressure in the cabin out of my subs). I had it in a prebuilt QLogic box, one of the old school ones that had a plexiglass front, and I believe it was the 1.25^ one, and that sub sounded nice in that. Also tried a slot ported prebuilt, and it got loud enough on 750 watts that my wife could hear me across the parking lot of her work when I came to pick her up lol.
In terms of loud and good sounding subs on the cheap, one of the loudest cars I have ever been in that sounded good was the Digital Designs Civic (I went in for a job interview and had a chance to demo it). With 3 8" 1508's, that thing made my ears ring and my eyes water, and sounded amazing.
I've sat in a Scion XB built by a Unique Car Audio in Arizona when I lived there, and that thing was full of W7's in prefab boxes, and even though it was loud and energized the cab, it didn't have **** on the Civic, with 3 small subs and less wattage than 2 of those subs were running off of.
I don't think you could go wrong with the Type R, or 2 of them, in a vented box. Or some DD 2500's or 3500's. I currently have a Kicker L7 12 prototype that was one of the first ones Kicker ever built, and it gets loud with around 650 watts, and can hit pretty much any note over 30hz-50hz with a LOT of output, but anything lower than around 25hz and it seems to struggle (Granted, I have it in a vented box that it came with from the guy I bought it from, that wasn't built to spec, and has a extremely thin slot port, so I haven't ever pushed it hard since I don't want to blow it, and I had no idea what it was tuned to)
Plenty of choices around, just check out some of your buddies systems and see what they are running //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
