Hi Gavotte, 

Thanks for posting your settings. 

1. Uncheck Full Ray Tracing because it is eliminating the memory gains made by GI interpolation. 

2. Unless you have overlapping transparency, set the Ray Tracing to 4. 

3. Turn Lighting Quality back to Good instead of Excellent. 

3D rendering is always a game of give-and-take. For a magazine article I was writing, I interviewed one of the lead animators on Monsters vs. Aliens from Dreamworks. He said that they'd love to use GI on everything but that there simply isn't enough time or computer horsepower to do it that way. So, they build lighting rigs to simulate GI instead. 

It's all smoke and mirrors.