they should be the same or pretty close...if you underpower a sub by a little your fine, most subs reach full excursion with less then there RMS power, RMS power if more a thermal rating of what the voice coils can handle. What sub are you looking at?
an audiobahn alum12q i got it cheap...so i put it in...is it a good sub? i want loud bass that can be heard outside the car...what would be a good sub to buy?
Well, Audiobahn isn't really the best stuff by any-meens, but out of them all I would say the Aluminum series are the better of their subs. Not sure how loud it will be, I think their supposedly more sq oriented, though I doubt your gonna get outstanding sq out of an Audiobahn.