Using one thread actually made it  look much worse!  (Weird.)  I am relieved actually, as using one thread instead of 8 sounded horrible.

I now have IDL at 64, and** Irradiance turned down to 10** which seemed to help quite a bit.  But there is still some noise when light from a light-emitting object is cast into a shadowed area.  Maybe I need to crank up my render samples to 8 (from 4)?  I'll give it a shot. 

In the meantime, here are my light settings:

IBL LIGHT : SHADOWS OFF, Ambient OCC ON (Strength = 0.7)

LIGHT 2 (SPOT) : SHADOWS ON (RAY TRACED) Blur Radius 3.0 (down from 5.0 earlier) Samples 20 (I think higher samples made it worse IIRC). Shad. Min Bias (0.8), Ambiamt OCC ON (0.7)

LIGHT 3 (INF.) : SHADOWS ON (RAY TRACED), rest same as LIGHT 2

Thanks,

Tim