I do not know what you are talking about?
All the links you sent links to a seller that says its z8300. Check your links again!. Though the link says z8500, the specifications actually say z8300!!!
Also DO NOT trust third party stores, Buy from the official Amazon store to ensure an activated OS and the best price. If you get one from third party stores, we cannot guarantee an activated windows.
Also in addition, the z8300 may look like a down grade from the z8500 but their performance difference is negligible. A 200MHz boost in CPU will probably give you like 10% performance?
Also thermal cooling is also a major problem, even the Mac Book Air throttles its core M when though it is under 2 GHz. You should worry about the heating problem instead of a lower frequency CPU.