i can vouch for the cerwin. it's a really nice driver. i have mine in a 2.25^3 box at 32hz. it hits pretty good low around 35-50. gets sloppy tho when pushed around 700-800rms. overall it's a good sub!
i have tried a vmax on both IB and ported. i must say that an IB install sounds HELLA nice. everything seems very linear. ported will give you better output but slice your low end but not that bad.