Same as last image, but I added my light meter. Let's talk about this:

The light meter has two zones. The middle zone is a diffuse light measurer. It is showing us that from most angles the scene is underlit. Only pointing right at the spotlight are we getting a good amount of light.

The ring around the outside measures specular light. It is telling us we are way underlit for specular. This is a good reason to add a specular-only light, which you were doing! Smart!

But I think the IBL is not only necessary, but we need MORE!

---

Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)