Iv heard 2 JL 8w7's in .8 cu ft each tunned to 30hz in an olds alero and it was impressive. They sounded good and got decently loud. They were on a JL 500/1
On the other hand I ran a DD1508 on 300 W RMS in a 1.46 Cu ft box tuned to 41hz and It got just as loud as the JL's and honesly didnt sound any worse, if not better. The JL's got a little warm after about 15 minutes of playing (tones though) and the DD would get a little warm after about half hour of music but nothing too bad.
Personaly I like the DD, especialy for the price but JL does have a sexy look to them. DD's are really beefy looking and if you do blow them they sell for more then the JL's and recones are much cheaper. Hope that helps.