Well, I was considering the same swap, especially if I had weight in mind when I get the project probe late this year... I've decided on an Audiobahn Tube enclosure (shown here- http://www.soundhabit.com/Store/prod...ProductID=1548
) You can probably find it for cheaper (or similar, but make sure its good quality) on ebay or elsewhere.
Then, load it up with either a JL audio 10", or something with a big magnet (at least 120 oz. magnet) And make sure the power output at least matches the amp you will use (if it's a two channel keep in mind you'd probably want to bridge it... maybe check out amps that have 1 ohm stable and subs that have 1 ohm stable...
In the end you can have a lightweight, small, yet durable sub hookup that'll hit hard and clean (if you get a good sub, and since its a 10) and should be more than satisfied from the outcome.