Originally Posted by ala_xfire

They did not fit without some modifications to the plastic holder assembly.
I installed Pyle PLPW6D 6.5'' 600 Watt Dual Voice Coil 4 Ohm Subwoofers.
The magnets on these puppies are about 3 times larger than the original Infinity's.

( easy way to do the hacking : drill around the area with a 1/4" bit as close together as you can, then use wire cutters to clip between the drill holes. Easy peasy Japanesy.
It ain't pretty, but it's all hidden so it does not matter. )