yep, disable mp all together. and i'd increase the ram for other apps to at least 1gb, maybe even 1.5gb or 2gb. this will help lessen the os from disk caching as often, which hurts performance significantly.
also, as you make changes and test rendering, watch the cpu levels with task manager. that way you can see how well the cpu(s) are performing directly and can help you determine better settings.
for example, if you notice that levels typically drop after several minutes into a render and disk activity increases, then you can bet that the os is caching to disk. if you look at ram and see that ae is only using 10% of the max ram cache (which is around 65%), then you could change the settings to give more ram to the os.
you can also do some tests with ae's disk caching enable and disabled. typically, if you have only one drive, you don't want disk caching enabled, but even if you have multiple drives, disk caching may have a negative impact on rendering, so it's good to test it.