If you are experiencing any clicks in stutters in the 3D Audio most likely you are playing a good number of audio sources in a highly reverberant room. The way to reduce the calculations which is causing the clicks or stutters due to CPU stalling, is to reduce the reverb tail. Create a custom virtual room and place the reflection materials in but adjust the reverb tail to be lower.
Also, if you are not concerned with having reflections on all your sound sources you can use the “Fast Spatialization” option. “Fast Spatialization” is strictly point source, so you get 3D audio w/out the reflections. A caveat also is that “Fast Spatialization” does not do have attenuation so if you go outside of the max range, you get a flat cutoff.