I decided to install a subwoofer in my leaf. I went through a couple of options before settling on a Rockford-Fosgate P300-10 powered subwoofer.
I used a Rockford-Fosgate 8 gauge wire kit to run power and ground to the setup.
It fits perfectly in the hatch against the back seat and there is just enough power wire in this kit to reach.
The system consists of 10" subwoofer in a sealed box with a 300W RMS class D mono amp. It can run off RCA or speaker level inputs. I chose speaker level and tapped both rear speakers for signal. It also has a wired remote you can mount up by the drivers seat to control the gain.
I think it sounds great and hits plenty hard at 50% gain in the leaf. The sealed enclosure sounds great and the tight bass works for rock, reggae, or hip hop.
Total package was under $200 shipped on ebay. $162 for the sub and $35 for the wire kit. This is solid real 8 gauge wire! Total install time was a couple of hours. I could do it again in an hour now thati know where to run the wire through the firewall and tap the rear speakers. If anyone is looking for good bass to supplement the factory speakers I think this is a great option.