Distance between speakers - are the physics what they are?

In now spending so much time in my kitchen it dawned on me that it would be a great space to set up some older components I had in storage.  It's great now having music in the kitchen but wish the speaker soundstage could be better.  The set up is using a pair of stand-mounted B&W 600 S3, which are "fine" but no doubt there are other similarly sized speakers that could perform better.  However. with the wall space I have to work with, distance between the any speakers would be, from tweeter to tweeter, about 3.5 feet.

Is not being able to put more distance between the speakers mean any upgrade would be a waste since the physics would prevent them from ever sounding as good as they should?