While I don't have specific suggestions for where to look for your winter coat needs, I wanted to say that most of the coats start appearing in stores in late October. From what I remember, Angie will post a fantastic 'coat' post with all of her picks from across the spectrum sometime in October.
It's a little bit early to be looking for coats just yet, though I can understand wanting to get it taken care of before the weather turns weird.
In my experience, Macy's is pretty amazing on the coat front. Granted, you can't always try everything on 'in store' that might be on their website, but they do have a great coat selection and some nice sales starting October and continuing on through Black Friday sales. In terms of puffer coats - I'd vote for either Eddie Bauer or Land's End - and they *also* have amazing deals during the Black Friday/post-Thanksgiving sales.
While I'm not sure about sizing, I am thinking that J Crew's "Lady Day Coat" might be ideal for a proper winter coat for you. I've had the J. Crew "Lady Day Coat" on my list for a very long time. Like you, I also need a proper winter coat - I have several trenches and one somewhat decent Talbots teal tweed-ish looking thing, but not a serious winter coat yet that actually fits me.
Meanwhile, you might consider:
Puffer: Eddie Bauer, Land's End, possibly Macy's
Wool Winter Coat: Macy's, J. Crew, Nordstrom, Burlington Coat Factory, Ralph Lauren, Brooks Brothers.
In fact, take a look at Ralph Lauren and Brooks Brothers sites this weekend, because a lot of retailers have some great sales going on this Labour Day weekend. If winter coats aren't exactly 'on sale' yet - they *will be* by the time Thanksgiving rolls around.
Also - you *must* try an Ellen Tracy Angora A-line winter coat and see if it's right for your style and if you like the fit.
http://www1.macys.com/shop/pro.....ker?ID=839
The price will drop during October and on through the Thanksgiving sales. The Ellen Tracy A-line coat is *fab*. I don't have one yet! I missed out on it a couple of years ago, and am *still* stalking it! I am not sure if you would rather a plus size or regular size, but I wanted to say that I can vouch for this particular coat being totally fab. It might look a teensy bit frumpy in catalogue or website photos, but I can tell you - it's not frumpy at all. Just amazingly slouchy and very stylish, imo. Very well made and flattering. If you can get your hands on one of these Ellen Tracy winter coats - you're set!