Robb - Solid Cactus is an Amazon Webstore Designer and can certainly help you get up and running on that platform in addition to your Yahoo! Store. Having an Amazon Webstore in addition to your Yahoo! Store allows you to easily get your products into Amazon.com for sale. You can learn more about the platform and our packages by going here:
Solid Cactus Amazon Webstore Offerings
Then of course, feel free to contact your EC to get rolling with one!