Did something like this at my first shop about 8 years ago in an RSX so its a little dated. As you can tell by the old school clarion source commanders on the sides and the old school slash amps:
Did this again about 3 years ago in an Explorer. Saved a lot of time by building a square box and then just bolting a glassed piece in between them ot add some depth and shape. Also the baskets on the w7's are bad ass...especially if you're getting the current 10 anniversary edition ones.
And heres another inverted one in an Audi. 3 10w6v2s that we had the baskets chromed on. Again really dated as you can tell by the old (but bad ass) rockford punch amps.
Hope that gives you some ideas. Got a lot more in my photos too if you want some more.