I'm also a member of the DMC, and just like in the stores. If Disney has put the movie in the vault, then you can no longer get it from the DMC.
Now, who you should buy from? For me it all depends on where you can get the best deal. I have found that sometimes the prices are little less on half.com than
amazon.com. It all depends on what you are looking for. They each have a form of feedback, so you can check out your seller. But I think half.com's is better. I have sold to quite a few people on amazon, but if you were to look at my rating on that site, I have had only 5 people leave a rating for me.
But you might want to also take a look at ebay.com, they also have some sellers who offer buy it now (BIN), so you don't have to wait for the auction to be over. Then you can just pay them with paypal, with your credit card. But just like half.com, make sure you check the feedback file. But really, it's not that hard of a site to use. If you can post here you can use ebay!
Typing in Beauty and the Beast on ebay, this is what pop up: (hope it works)
http://search.ebay.com/Beauty-and-the-beast_DVD_W0QQcatrefZC12QQfromZR8QQfsooZ1QQfsopZ1QQsacatZ617
Almost forgot! Make sure that the sellers you are buying from are selling the USA versions of the DVD. Their are some sellers, on all three of these websites, who are from the Asian coutries, who are selling either, their version of the movie, or pirated movies. SO CHECK EVERYTHING CAREFULLY!!!