When growing these outside of their native habitat, is it best to start our own plants from seed or are transplants started elsewhere and grown to shipping size a good bet? Does it make a difference either way?

The biggest factors are your budget and level of interest. Suppliers of alpine plants will have taken pains to grow their plants in the required soil conditions, so you won't find the problems people see with, for example, regular perennials grown in extremely peaty, hydophobic mixes that dry out and prevent root growth into the surrounding soil. I'd suggest purchasing some of the easier alpines as a start.
On the other hand, if you are reasonably proficient at seed-starting (and patient), you may want to start there. Instead of buying one or two of a limited number of species, if you start seeds yourself, you can end up with a few seedlings each of a larger number of species, allowing more experimentation in planting. (However, if you are not experienced at seed-starting, I don't recommend jumping into it whole hog - failure and frustration turn most people off pretty quickly! Buy plants, like I said! ) I grow most of my plants from seed (and this is pretty common among alpine gardeners) simply to sample the range of species not available from even the alpine plant specialist vendors.

Thanks, Lori.

I'm getting pretty good results with winter sowing seeds, so I'm going to try some of both, I think. Just a few transplants though since I need to see when exactly they're shipped and how they'll handle the transition. From what I've read so far, it's been suggested that the best (maybe only?) time to plant out would be in early spring. We go from frozen to hot very quickly, so timing might be critical. I just don't know as yet.
I usually like to set out regular perennial transplants in the early fall here, when there seems to be more of the "just right" settling-in weather, but I'm not sure if it would be a good time for these types of plants.

Generally speaking, it's a good idea to use a very permeable and lean soil mix (i.e. large proportion of sand and grit, compared to humus or compost, if any) for your rock garden/alpine seed starting.
The alpine plant specialists I've ordered from (Beaver Creek, Wrightman's) only ship in spring, so that should work.

Edit: Correction - Beaver Creek does not only ship in spring.

Wonderful. Beaver Creek is one of the nurseries I hope to order from. I haven't browsed through Wrightman's lists yet.

You guys may already know all about it, but if you DO wnat to start a few things from seed, Alplains is totally awesome. I haven't bought from them for myself, but I did once for a friend.

Amazing selection of alpine wildflower seeds!
http://www.alplains.com/

In 2011, Alan received the Marcel Le Piniec award (North American Rock Garden Society). That award was for "enriching and extending the range of plant material available to American rock gardeners."

Correction: Shipping from Beaver Creek is not limited to spring.
Yes, Alplains is a superb source for seeds of North American alpines and others.
I've been ordering seeds from the various Czech seed collectors -fabulous selections - as well as from NARGS and SRGC (Scottish Rock Garden Society) and Alplains.
Here's some info from an excellent source of info - the North American Rock Garden Society (NARGS): https://www.nargs.org/forum/se...

Thanks for the links and information, Rick, Lori. I confess that I have a tough time navigating the nargs site most of the time. If I could figure it out and get comfortable with it, I'd probably join up.

When I lived in the US, I used to mail order rock garden plants from Arrowhead Alpines in Fowlerville, Michegan. I loved their printed catalog, which was full of interesting information. Now they have a website, www.arrowheadalpines.com, that looks equally fascinating.

I've been perusing that site quite thoroughly.

I have seeds due to arrive shortly; I'm getting so excited about this project! Heh-heh, one (at least) of the plants I ordered seed for is considered very difficult. I'll need a lot of advice and a ton of luck for that teeny-tiny plant!

I've ordered from Arrowhead Alpines and Alplains several times, and have always been pleased. Like Lori, I am an active member of the North American Rock Garden Society (NARGS) and the Scottish Rock Garden Club (SRGC). I tend to be more of a seed sower. Alpine seeds can be easy or difficult, depending on the species, and you'll thank yourself again and again (and again) if you keep good detailed records to look back on.

... and there are lots of seed-starting records that you may find useful for seed germination and growing tips over at the NARGS site.
Here are some links to start you off (there's much more):
https://www.nargs.org/forum/se...
https://www.nargs.org/forum/se...
https://www.nargs.org/forum/se...

I had an opportunity this summer to shop at the actual nursery this summer at Arrowhead Alpines. Contact me privately if you would like to know my experience