i dont know if youre still thinking of getting an 8"er, but if you want one for cheap, i have a couple kicker 8" tubes (substation 80 model) that are actually quite loud for their size. One of them has a broken baffle, so if you want both of them (if youre even interested that is), youre gonna need a box, or just use one and ill make one onto a vented box for my dad's truck.
The best part of waking up is kickers in your trunk!
You were asking about some input on quality 8" subwoofers. We use Digital Designs unless someone brings in their own equipment to have installed. It is a no-compromise brand with the best parts that money can buy put into each specific price range series. The 1000a series is the only that have an available 8" frame size. This is the same 1008a that we put in the demo vehicle '05 Mini Cooper S in a 0.75 cubic foot ported enclosure tuned to 42Hz that did a 141.7 TL measurement on the back 2 channels of a DDC4 4 channel amp. That's pretty retarded output from a little subwoofer. I, ofcoarse, highly recommend the 1008a to you for what you described as your taste. The same vented enclosure would be my recommendation as well. It's tiny and very effective. You can check them out at http://www.ddaudio.com