Yes, I think a lot depends on your activity level. What I wear when I am standing around birding in cold weather varies greatly from what I wear when I snowshoe!
I do get hot easily as well so unless it is really windy or really cold (below 20F) I would not wear a base layer on top. What I have been wearing is a Lands End Heat Crew top, sized up so I wear it as a shirt and not a base layer, a thermal weave or light Polarfleece 100 pull over on top of that, a fleece vest (again Lands End PolarFleece 100) and a wind/rain layer. I do wear a base layer under my jeans and have had good luck with the HotTotties brand. If it were windy or very cold, I would add a base layer under the heat crew shirt. I have both the HotTotties top and a merino wool one I got at Costco last year.
I have Smartwool glove liners I wear for everything. They are not quite warm enough for standing around if it's windy or very cold but they are fine if I am active or just in the car or popping in and out of stores. The Smartwool liners are also good even during light chill times in summer. They wick well. If you are outside you will need gloves to wear over these as well. Haven't shopped gloves other than the liners in a long time so no recommendations. Definitely go with liners and gloves and try the gloves on with the liners.
Socks - I am a proponent of the Costco Kirkland brand of merino wool socks which my local Costco has now. Very inexpensive and a good way to see if you like Merino wool.
Jacket - Unless you will be in the cold a lot more than your vacation, I would not spend $400 on a jacket/coat. I would look at Columbia Heat shield jackets. If you have an REI in your area I would go and look to see what they have. Often the sales people at REI are pretty knowledgeable. I have a Marmot Precip which I travel with in summer but also use in winter during rain or snow over a fleece vest. I also have an old Goretex jacket that I use at times. I do suggest you look for a jacket with pit-zips as well as a front zipper that will unzip from the bottom if that makes sense. That is the only thing I don't like about hte Marmot, it only has a one way zipper and sometimes I want to vent a bit from the bottom of the jacket. When you say big parka do you mean you will take a parka you currently have in addition to another jacket?
Hat - My favorite winter hat is an Outdoor Research Winter model Seattle Sombrero which is waterproof and fleece-lined. My family assures me it is the dorkiest hat they have ever seen. I like it because the brim keeps the snow out of my eyes, it has a good chinstrap which keeps it on in wind and earflaps. I just looked at the OR website and it looks like the model I have is now called the Snoqualmie Sombrero. It is expensive and you might not need this much of a hat. If your jacket has a hood you can probably get away with some kind of a beanie under the hood.
Gaiter/face mask - For me, I may be warm but my face gets cold easily. I always wear a neoprene face mask which covers my mouth, nose and cheeks. I also have a polar fleece neck gaiter which I cover my neck with.
If you do go with any of the Land's End stuff, sign up for their emails and you will get offers for 30-40-50% off nearly every day. That is also one of those websites where if you sign in, put stuff in your cart, then leave the website you will often get an email reminder with a code for a discount, so it is worth it to play around with that. I think their fleece is good quality and is pretty inexpensive compared to Columbia or North Face or one of the big brands.
Have a wonderful time!