Wouldn't worry too much about a capacitor. Do the big 3 instead.If you intend to use a one channel amp at 2ohms you need dual 2 ohm subs.Use dual 4 for a two channel amp.
What vc's dual 2 or 4 ohm? I've got two of the same subs running off a zx15001 at two ohms (dual 2 ohm vc's).Does pretty good.Not too sure about subs box and other crap that cheap though.