JL stealthboxes are around $500-600 and you cannot purchase them online.
If you want a good stealth box for a lot less I have a contact on corvetteforum that makes his own custom stealth box out of MDF that fits in the trunk well. This way you can run whatever sub you want and even go up to a 12" sub, which you CANNOT do with the JL stealthbox.
His box is approximatley $150 shipped and he cuts the hole for you if you tell him what sub you are going to run.
I personally went with a JL 10W6 for my box. Check out my pics in the gallery of the sub inside the box.