If I "buy"
http://www.amazon.com/Life-Mississip...dp/B0084B1X2Q/ (a book with supposedly KFX and KF8 enabled), I get .azw file about which Calibre claims to be a MOBI and `file` that it's "Mobipocket E-book version 7". So, no, you'll get just what matches the firmware Amazon *expects*.