Without wanting to rain on your parade, I think you should give a serious look to hosted ecommerce solutions like Shopify, Redbubble, and Etsy. Any of them should give you all the features you want and you'd be up and running in a few hours rather than a few weeks or months, plus you'll be able to take online payments with reasonable certainty that they'll be secure (and a well-insured corporation to blame if they're not).

Not saying you ought to go that way, just that it would be a bad idea to not at least investigate those.