Jelinda, what a great start you have on your wonderful rock garden. I am very excited about seeing from the beginning, and getting to watch it grow to maturity.
When does your growing season begin? I see you are in the south and already have some nice warm, spring type weather. Still freezing at night.
This would be a great time to get your new semps into the ground, so they can get a head start on root growth, before the hot weather arrives.
I have received new semps and sedum in January, potted them up (ground was frozen) and set the containers outside in full sun. Great success, by spring/summer they were going great guns.
A few great places for semps:
http://perennialobsessions.com...
http://www.squawmountaingarden... has some nice plants on a special right now. Right side of page click on Specials, down the page a bit you will find the hardy succulents.
http://northhillsnursery.com/
http://www.youngs-garden.com/