Perhaps, but Honda is the manufacturer, and Accord is the product, whereas "nano" is merely a modifier of "iPod." The term "Honda" isn't actually part of the name of an Accord anymore than "Apple" is part of the name of the iPod. I think it's a slightly different situation. Interesting point, though.
How about "There goes two Honda Accords DX" vs. "There goes two Honda Accord DX's"?
Yeah, we'd say "DX's." Is it technically accurate, though? This is the closest parallel, though.