my mistake i missed the 2 mags sealed part vs 2 bms ported... just out of curiosity why not port the mags?
and if you go sealed i don't think youll notice much difference in output between 1800 and 3000watts, i know thats a broad statement but in a perfect world double the power is worth 3dbs, so 3000 watts vs 1800 your looking at between a 2.0 and a 2.5db difference, audible but not drastic
however i would bet money that 2 mags ported would be louder than 3 sealed, and you could keep your orion, and only have to buy 2 subs instead of 3(if they come in dual 4ohm that is) save you some money at least...