go with the large. As for a shell, you may want to consider a rain jacket, such as the Mountain Hardwear Cohesion or Marmot Precip. They will keep out any rain/snow, but won't add much in the way of bulk (lighter than hard or soft shells), or add much warmth - but still have pit zips just in case.

I'll toss in a second vote for a large Down Sweater based on your measurements. Still won't be bulky or oversized, and I think you'll be happy with the additional length and room in the chest. I wouldn't worry about overheating with this thing on it's own, the temperature range is awesome. I run warm also, and when it's cold I've got to be moving quite a bit to take this off. And if it's super nasty out you'll love having this under your hard shell, tough to beat. It's definitely the perfect jacket for what you're looking for, and as for a hard shell I would recommend the Patagonia Shelter Stone. For freezing rain or wet snow it's one of the best out there. (I'd shoot for a large there as well). It's got pitzips and will keep you dry in the worst conditions a New York winter can throw at it. Hope this helps!

6, 190, 16-16.5, 35 sleeve & 34 waist, 41-42 chest and I went w the large. Definitly room to layer under it. Not really sure that I could squeeze into a med and still have the right sleeve length though. I hate sleeves that ride up on a jacket Given the jacket weighs next to nothing, you could order 2 and return the other....should only be a few bucks to return plus the hassle of mailing. If you're concerned with overheating, whatever hardshell you choose, I would make sure it has pit zips. You might even try a soft shell like the ascenionist. It doesnt have pit zips, but it would breath better than a hard shell and should be decent protection in all but the worst rain....then again, if its raining that hard and you're wearing the down, its probably coming down as snow. Quite a few sales going are on the ascenionist.