2 re8s or 1 dd1508 both tuned to their recommended ported specs (RE8s need .5 cf @ 32hz each dd needs 1cf@ 40hz)...which would sound better?? Both options run with 500mono kicker amp

 

I've never heard the DD but I have 2 RE re 8's in a ported box that pound harder than most of the civics I pull up beside, on 400 watts

 

Hard to tell..if they were both tuned to the same freq, then the 2 8's would be louder with the same power, but when you tune higher, the output can increase significantly. As far as sq, both are good sounding woofers, so you should be happy with either.