.....visit ADK computer website....they are most knowledgeable about what will work....and what will NOT....with After Effects....it can be complicated for a novice to understand. The new "2014 Creative Cloud" was released today....it included a MASSIVE improvement in speed for Premiere Pro....I am not sure about After Effects,( which does not rely on the GPU as much...except for "ray-tracing" ). Eric at ADK can advise.
What media are you dealing with in AE. Normally you want a 6 Core and 32GB of ram ideally for AE work for standard workflows and complexity. The X79 platform is the place to start. The GPU has little effect on most workflows with AE since Ray Tracer is only used for certain processes. CPU and Ram are you 2 primary system components and an SSD drive for the OS.