if space is not a problem then put it in the 4.0 cufy ported box. If you want a sealed then basically it really doesn't matter to much on box size. The 2.25 cuft box will give you more impact but the lows won't be as loud as they would in a 5.0 cuft box but it's not to big a dif. The 5.0 cuft box has more of a punchy low loud bass sound. It's your choice.