The 10w7 is kind of an annoying sub. I had it for a short time mated to a 500/1 in my 350z. It is a very inefficient speaker (thus the mate to the 500/1 which is a good match), and it is not very musical. On the upside, its pounds like no other speaker I've heard and takes a ton of abuse.
A better match to that 500/1 is a Diamond Audio Hex 12'. I was really happy with that combo - hit all the low notes I wanted, and remained musical throughout.
JL does make a remote dial for the amp, but it only controls a boost, not volume. I think you can get inline volume controls, AudioControl may have some device that does this (havent researched them in a while). You can , of course, always use the gain on the amp to lower the sub volume.