The Aluminum is gonna be the cheapest. Depends on the model, but you should find them for under 200 shipped. The RE SX is around 250? Not quite sure, it's around there. The Type X 10 should be around should also be around 240 - 250 shipped off ebay. I would say the SX would probably be the best out of them all.
Will the 10" SX have to enough to take out a 12" L7 thats in a small sealed enclosure. Is there that much difference SQ wise between a Sx and a aluminum. The sub will be in a toyota pickup reg. cab. Thanx