IMO, S. gigantea is not an anemone you want to get without seeing it in person first, unless you live out in the sticks somewhere.
Most online vendors aren't able to tell a healthy gigantea from a "soon to be dead" one. Since most of the gigantea that come in fall into the later group, the chances of you getting a good one from an online source are very slim.
Be patient, shop the LFSs and let it be know what you are looking for.