[Andy Taplin]"Can I stay on QT 7.5 (I have a lot of Media 100i footage I need to access)? "
You should stay on QuickTime 7.5 if you want to use Media 100 i footage. QT7.5 works fine with V13.
[Andy Taplin]"I have a Kona 3 card - do I need to upgrade from 6.0.1? "
You need to upgrade to the Aja Kona V6.01 drivers. But do not install the firmware update, which can be run after installation, since the new Kona3 64 bit firmware is currently not compatible with Media 100.
[Andy Taplin]"I currently have M100 and FCP on the same boot drive working perfectly - be nice if it stayed that way! "
It will, as long as you do not upgrade to QuickTime 7.5.5. The new Apple ProApps update with FCP 6.0.5 does require QuickTime 7.5.5, though; if it is okay for you to stay on FCP 6.0.4 you will be fine. But the ProApps update will not get displayed in the Software Update anyway if you don´t install QT7.5.5.