the more plugins you have the high the cpu has to work, its like the cpu and the gpu is not handling the extra load of graphics and the plugins,
at could be as simple as the ragehook haveing problems with one call out and keeps shuttering when it adds it
i have the same problem i remove half of the callouts and then tryed it, and slowly downloaded and added each one again trying it as i go untill i found the one playing up
but as you say the cpu and the gpu are a good one,