You've been through EVERYTHING on that page, and no joy yet?
The only recommendation I can make based on the available information is to leave 4 cores for other applications.
Use less cores, but enable the disk cache. Many times this has much more impact, if you simply allow AE to cache to disk. Of course it stil ldepends on teh nature of the project, but it's worth trtying. Also, since any cores beyond No. 6 are virtual cores, you are causing extra overhead when attempting the virtual cores. This may have a noticable impact, too. If you get my meaning: Just because you have lots of RAM, doesn't mean that you must/ can use MP in teh way you desire...