It would probably be quicker to list the organized New England centuries I haven't done by now... The only two in New England that immediately come to mind that compare to Mt. Greylock in terms of difficulty are the Mt. Washington century (mid August, northern New Hampshire) and the Great River Ride (early October, southern Berkshires in Massachusetts). As a bonus, the Great River Ride allows you to visit Peru again!

My regular riding buddy and I have a special contempt reserved especially for Peru. It is just mean to send anybody there late in a ride. (Random fact: www.weather.com does not acknowledge the existance of a town called Peru).