Uhh...Any case with enough space can house 2 psu's, provided you're willing to cut out the back panel to let the extra one vent properly. With a full tower like a 750a, mount the new one upside down on top of the original after a little cutting/drilling. You can and may need to get more creative, depending on the available space.
Run a search on this forum for the info on how to wire it up so that they work together transparently. Quite possible, not a real big deal.