"I would conclude that the sole basis of atheism is the lack of empirical evidence and the inability of scientific reasoning to prove the existence of a separate spiritual plane of existence. Would this be correct? "

I appreciate your sincerity, but you really have that ass-backwards. The 'religious' are unable to 'prove' (except in their own mind, by convoluted semantic jumbling and smearing of concepts) any of their complex convoluted mumbo jumbo, which by their OWN definition 'is beyond human understanding' (told you I was brought up fundamentalist Lutheran!), so they just accept it 'in their hearts' on 'faith'. To see a current topical example, you might like to wade through Conrad's thesis on 'FREED Folk Music' where he insists as a matter of 'faith' that getting stonkered with gallons of 'bier' on every musical occasion is necessary for 'the release of his muse'... :-)

The one with 'faith' KNOWs, the atheist just 'not-know's - as I said "What part of No is so difficult to understand?" which has now become a fairly standard answer to the "Creationist/ID proponents' whose intellectual flailings about remind the student of the history of scientific progress of things like 'the aether', orgonne, the musical theory of the crystal spheres of the rotations of the planets, the history is littered with ineffectual attempts to grasp understanding..

I've input here on that before, so I'll let others have a turn, or I'll be back later, supposed to be mowing grass, really ... :-) ...