I use a Linn AV 5150 which is downfiring but the manual clearly shows how to pull off the stand and mount it to be front firing (i.e. in and enclosure/stand/or the 'little niche' your wife will allow.)
It's an interesting question, given that you can make the space for the sub any size, assumably any shape as well, you should be able to use any sub, given the shape of the space is good. You'll need to figure out how to properly shape the space, but, once this is right, you probably could use any sub you like!
This thread just reinforces how great single life is to me! My girlfriend only asks wonderful questions like do they (new speakers/amps/etc) make you happy?
Good luck, you've got your work cut out for you figuring out the best shape and size alcove to make!
