Looking good! I would put that purp there outside.
I plan on doing that this weekend. That S.Purpurea was a lowes plant and has been sitting in that windsill for one month where it gets 5+ hours of direct sun and under 16 hours of fluorescent lights. I will put it out on my porch with my Judith Hindles where it will get allday sun.
Here is a before and after picture:
Before:
After 1 month later: