That's a pretty long ride. If you are coming from yonkers, on a one day trip, going through amenia is probably not the way to go. A couple of notes:
First, I would avoid Rt 7 like the plague from the Rt7/Rt25 junction up until the Rt7/Rt202/Rt67 junction. Lots of high speed traffic, construction, and no shoulder to speak of.
Second, going around Candlewood Lake from the north Rt37 & 39 will give you some pretty long nasty climbs. Going around the south through the center of Danbury isn't as nasty, and if you take 133 to bypass rt 7, you'll get a long climb, and some great views at the top--and an absolutely awesome chocolate shop at the center of town.
Third, lots of hills. It is pretty much impossible to avoid hills on an E-W rt in CT. N-S, north of Kent you rt 7 follows the housatonic, and that will take a lot of the bite out of the hills. Rt 4 has a big nasty hill by Mohawk Mtn ski area, which you wouldn't be able to avoid coming from Amenia, and 202 has a whole bunch of hills.