spurium voodoo------------I've had this one for years. It isn't a fast grower for me, but might be for others.
silverfrost---------------------- Should work.
selaskianum spirit fastrax ---This one looks interesting also.
rubens lizard ---- ---------------I don't know anything about this one, but it is sure cute, and a low, tight grower from what I read.
forsterianum oracle ------------ Should be a tough one.
If the seeds are cheap, I would get as many of the low growing types as you can and see what makes in it your growing conditions.
I really like their S. 'Red Carpet'. : )
Wish they listed what is in the low growing Rock Garden sedum mix.