Open air subs are built to not use a box. from someone I know who has one, if you are outside the car, you don't really hear it, but inside sounds nice. and about 8" subs thumping, if they can handle the wattage, it's all about the amp you got powering it. About a good 8 inch sub, how much do you want to spend? I mean, you could get a Kicker Solo-Baric S8L7 it's 4 ohm and can handle up to 450 watts RMS, 900 watts max. (that'll thump) and it only needs a .66 cubic feet ported box. but it's gonna run you about $230 for just the sub (no box).