Generally speaking, your best option is going to be to stick with Totem, and specifically get the center that matches the Mites, the Mite-T Center.
I plan on later on getting larger speakers and turning the Mites into the surround speakers
However, if you know which speakers you intend to purhase for use up front after you move the Mites to the rear, it may make more sense to buy the accompanying center for those. But again, that would assume you know which you plan to buy for your fronts, which you may not have determined yet. Going this route would allow you to avoid having to get another matching center down the road in addition to the one you get for the Mites now.
