It requires 2.66 cubic feet of air space for each sub, and it says it needs a 4 inch by 10 inch port. I don't believe the port needs to be that exact size!
Heres the specs on sub,
http://www.rockfordfosgate.com/rftech/library/2007/5_Subwoofers/P3D215_revA-TS.pdf
Do you think this one would work fine?
http://www.shipsound.com/product_info.php?products_id=101128&&osCsid=t3kugevflmpjicauva27fa38d5
Heres the specs on sub,
http://www.rockfordfosgate.com/rftech/library/2007/5_Subwoofers/P3D215_revA-TS.pdf
Do you think this one would work fine?
http://www.shipsound.com/product_info.php?products_id=101128&&osCsid=t3kugevflmpjicauva27fa38d5