Here's a link to the Crutchfield page for those subs. it recommends a 1 cube enclosure with a 3" x10" port for each sub. by the way you would use the front mount displacement in most cases, unless you're bolting the sub from behind.

http://www.crutchfield.com/S-7FKlWlbLQhB/cgi-bin/ProdView.asp?g=520&tab=detailed_info&i=500SWR1021# Tab

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2004 300M SPECIAL
Alpine CDA 9833
Alpine Pxa-h701
Alpine Rux-c701
Rockford fosgate p400-4
Rockford fosgate p4004
Hifonics BX 1205D
JBL c608 GTi
JBL p963
Infinity 2.5" center channel
Alpine type R 12"(2)
200 amp alternator
yellow top battery
0 awg power and ground (welding cable) 300 amp anl fuse
all active SQL set up with 2000 watts rms