Sundown will rattle your doors where ever you face them lol, especially if you are getting two subs hahaha. Though with good sound deadening material you could really reduce on the rattle. 2 15s will take up a lot more volume than 2 12s, depends on work space. On the bandpass issue, I have not yet seen any X-15 in those enclosures.. As for now we will all just wait for the dimensions as it will be difficult to advise without them.