Fi q 12in ported or 15in sealed

Here's the deal... The car is a 2001 chevrolet s10 blazer 4 door and i currently have a 12in l7 kicker (4ohm dvc) with an enclosure of 3.75^3.ocft @ 35hz... powering with an Sundown audio saz1000.1d the sub is currently gettinh 600rms on a 2ohm load... i'm looking for something with quality and want it to get low and loud. i've came to a conlusion to go with an Fi q, the only problem is i don't know whether to go with a 12in fi q 2.5cft@ 32hz or a 15in fi q with an 2.6cft... not sure of options since havn't made up my mid on what size nor know what options to go with with either setup... i will be running the amp on a 1ohm load to feed 1k rms to this fi q. i'm leaning more to the 15in sealed since i can get more quality and loudness since it's bigger oppose to the 12in sealed...... but not sure... i listen to diff genras of music but mainly hip hop, trance 'n r & b I'm sort of limited on cargo space which is why i think of going 2.6sealed on the 15in... any ecpirenced user that can give some feedback would be great!!! thanks