As you have eluded to, the bendix gear in these Denso starters has been problematic in every Vibe/Matrix/Corolla/Scion/Honda and on and on and on, and should be the first place you investigate. Secondly, it could be the timing gear actuator, but if you are out of warranty, which you are, start with the simple things. I betting my mortgage it is the starter. Check all the videos on youtube. I will admit after watching many of them over the years and having the problem on two of my cars (Vibe and Fit), that your noise is a little lower in tone than the typical metal on metal scratching noise upon startup indicative of a failing starter. But I'm sticking with the odds.....the starter.
Live it up: There will be plenty of time to be old when you die.
** 2009 Vibe: 1.8 liter automatic **
** 2010 Hyundai Elantra Touring **
** 2007 Honda Fit Sport **