As I've been saying a lot- build your own IB Sub. If you want to get fancy, you can really have at it- I was thinking of going so far as to making it configurable by having a panel where all the voice coil connections terminated (by woofers are dual VC) so that I could configure them parallel, serial, add resistors, etc.
The other DIY thing as far as equipment goes is the modifications you can do to existing equipment. I'm going to be modifying my EP2500 Amp to slow and reverse the fan speed (the cult has links to doing it).
I might add some LEDs.
