Both boxes are older speakers, which I don't use anymore. They use a 10 inch driver and two tweeters. But Im thinking in open the hole to fit either two Shiva's or two Tempest and then seal them. Other than reinforce the boxes I can't think of another reason why not. As you probably know by now, I don't know know a thing about parameters like Xmax and such things. I know that the box should be made around the driver, but, if I already have them, what should I do?