From what I've been able to gather it appears that Kindle for PC is your best (or unfortunately for you worst) case of an emulator out there. There is a Kindle Developer's Kit (KDK) that you can sign up and request to be a part of. From their site:
To become a part of the KDK limited beta, request to become a beta developer. Accepted beta participants will be able to download the Kindle Development Kit, access developer support, test content on Kindle, and submit finished content. Those wait-listed will be invited to participate at a later date as space becomes available. The Kindle Development Kit includes sample code, documentation, and the Kindle Simulator, which helps developers build and test their content by simulating the 6-inch Kindle and 9.7-inch Kindle DX device on Mac, PC, and Linux desktops. Content submission is free during limited beta.