I buy everything photography and computer related from B&H. They have a physical (actual store you can walk into) and online presence. They have superior customer support (answers, service, specifications, recommendations, etc) and fantastic prices
In response to your question, I recommend contacting them directly. I believe that what you are reading wrt "returning" a computer is that once you buy it, you can't return it because you changed your mind. If there's something wrong with it, they will honor the warranty and provide a new replacement - check with customer service. I had a similar issue where the item was "special order." In the description, it stated the item was non-returnable. When I spoke to them, they clarified and provided the same explanation above.