Crepe Myrtle

I planted two Crepe Myrtle’s one year ago. I thought that our horrible winter had killed them, but each is now growing back with shoots from the roots (or below ground anyway). Examining mature trees near me, I want to have 4 or 5 trunks, maximum. There are currently about a dozen stems from each tree.

What should my strategy be? How many stems should I remove right now (or rather this winter, after the leaves fall)? Is it better to wait a few years for all the stems to become stronger?