IMO, a proper IB sub setup is one of the best sounding you can put in a car. Note, I said proper. They are a ton of work to get right. You have to have a very solid baffle, and it must be completely sealed from front to back (no sound can leak through. I did my 5.1 lexus this way, and I ended up building a custom particle board / fiberglass rear deck, and used about 20 lbs. of clay to seal it from the trunk. Sounded awesome, though.

That sound quality is also subjective. A properly designed IB will be super accurate, and super linear, but they don't typically handle a lot of power, or get as loud as an enclosed system. If you are looking to 'pound' go with a box.