Few RAM/CPU usage, minimal framerate/performance

Animation playback is very slow (11/24 fps) in an file with a meshdeform rig (600mb .blend). But there is only 15% of ram/cpu in use. How can I achieve optimal performance by using all of the computers power?

Thank you

CPU (Processor):Intel Xeon E5-1650, 6x 3.20GHz
Mainboard:ASUS P9X79 WS, Intel X79
graphics card: NVIDIA GeForce GT 610 1GB - passiv
RAM:16GB Kingston DDR3-1333 (2x 8GB)
SSD:128GB Corsair Force GS
hard disk: 500GB WD Velociraptor (High-End)

Most depressing thing ever; apparently blender viewport playback system isn’t multithreaded, which means only one (of my 6) cpu cores actually will do stuff -> 16%.