"The frequency won't be 15hz, that is the resonant frequency of the subwoofer in free air, the frequency changes when in an enclosure. The resonant frequency of that sub in, say, a 3.5 cu ft enclosure will be around 40hz for that sub. Yes, it will handle the entire sub frequency range very well sealed".
"Mo, sealed you will hit closest to the resonant frequency of the cabin due to a flat response above around 40hz. Ported, that will depend on the cabin gain, but you'll likely still hit the loudest higher up due to the low tune of the box. Basically you can expect similar results with both since you'd have a low tuned ported, you'll just get more output down low with a ported box".
How much is more output say at 3.5 cu ft. at 22hz-24hz ported?
so with my available 250g4 800rms amp i should stay sealed at 3.0. The main thing is i have ID cxs componants for the doors for my front stage and i dont want overkill of that but i wanna hit hard enough to feel for RAP and differant complex bass. I use to run 2 12w6v2's sealed and it was very good SQ but with good spl. Will i get more spl with this setup sealed or not?
If you want to outdo the 12W6v2s you had, then ported is the way to do it IMO. A 15" has less surface area than 2 12" subs do, although the Avalanche has more excursion, you may or may not use it all and it still may not offset the difference in surface area. Ported would be a definate improvement in SPL. Sealed Avalanche vs two sealed W6v2s, I'd say the Avalanche would either match them or barely outdo them, nothing substantial.