I beg to differ on this , especially if we are talking about putting a single sub in an enclosure built for 2, from JL, and building an enclosure with the correct airspace as an "amature"
Plus if you use a design program, and measure the area you are going to put the sub in, you will get better use of your trunk/hatch space (in most cases)

Just my 2Cents though.. I have been building enclosures for 15 years for my own systems. I would not consider myself a pro at all.. and some of the pre-fab enclosures do sound good ( also, depends on your listening style.. because most prefab enclosures are tuned pretty high, especially for smaller subs) But I would much prefer having a non pre-fab enclosure, tuned where I like it.

 

alll subwoofers have a low and high enclosure volume rating. so lets say that the jl 10 takes minimum of 1.5 cu. feet, and maximum of 2.5. the 1.5 would be for tight solid bass and the 2.5 would be for deep rumbling bass. also the distance it takes for a subwoofer to create bass in the hearing spectrum of a human, for the best sound anyway, takes lets say 8 feet. if your sub faces the front of your car it will make the bass complete out in front of your bumper, if you flip it around facing the trunk now it travels 2 feet bounces of the trunk and by the time it hits your ear it will almost be to its full potential. hope this help even though its not quite what was asked

 

Deffinatly dont do anything to the JL box, those things are alot of money and u can get alot for them. They are the best you can have for that particular sub. My store sent me and some of my people to JL's factory in mirimar florida to see their building processes on their High Output, prowedge, and powerwedge boxes, and they spend lots of time on all those creations to make sure that that box makes the sub(s) that come in it sound the best possible that it could sound. Besides that, their boxes look really good and clean. But if i were in your sitchuation, if theres nothing wrong with that 12W3V2, then i would deffinatly pick that up. you cant beat that price on a normally 199-249 MSRP sub, plus the box.

 

picked up the 12w3v2+box for 130. . .now to sell the jl box. . .it's on ebay as we speak. . .hopefully it sells

 

good choice. good luck with selling it