right now i bought 2 cw12, i have one running in a sealed box with 400wrms of power lol.. .not enough power

i would like to build a ported for everyday use but just dont know how to go from here to tune the box ... well really i dont know what design i could do ( dont have any programs)

i was wondering if someone had experience with these subs. they recomend a 2cf with a 4inch x 9 inch port i think but is there anything better for those subs... like a bigger box more ports ( or does slot port sound better than round??) i have about 50"Lx15"Dx15"H to play with also what would be a good frequency range to tune it for good sound and spl i would like to hit at least 135db or higher

any help would be great thx