I have an existing Atahualpa theme http://www.speakwithoutinterruption.com/site/ and want to see how my site would look if I selected any one of the various "Magazine" themes offered. How can I preview these themes - and how my site would look using them - before I made a final decision to switch?

any one of the various "Magazine" themes offered

I'm not aware of any magazine atahualpa themes. can you point me to what you are talking about

As an aside I noticed the slow loading of your header images and found they were over 3Mb in size. One was almost a whopping 5Mb. You might want to think about optimizing them for the web.