Just got back from doing this as well as some time in Ireland and NYC. We stayed at the Culloden House near Inverness for 3 nights (took the train up from Glasgow) and had Highland Tours (highlandtours.info) drive us. One full day for the Speyside Whisky tour and one full day of seeing the castles, fort, and battlefield around Inverness. The Culloden House also has other drivers to recommend. Great fun.