JLs all the way
JL audio makes bad a#$ subs. I wouldn't even think about getting anything else. Their w0 series is for beginners, w3 series for SPL, and their w6 series is for SQ.
JL spends the most money on research and gives you by far the best quality. While other subs may cost half as much, JLs will last twice as long. I'd rather go through one sub and spend a little more up-front. Not to mention how tight they are......
Eclipse makes some good Aluminum and Titanium subs, but they cost an arm and a leg. Besides, do you really want to have metal on your speakers that is stronger than the metal frame of your Explorer?
I'm talking about the titanium now.
Karl