i had a pair and they definately sounded better ported. you can call alpine and they'll give you the specs for a slot vented box, i think it was 1.5cu ft. each side tuned to 32hz. if you want it boomier go ported.
but i agree with true story. in the ported i still wasn't really happy with them, so i got two w3's in a sealed box and they sound alot better in my opinion. bass is just alot tighter with the w3's.