After Effects Slow Down Perfomarnce even with a Great Computer

your new computer probably has more cores than your previous one. 
that, and 16 gigs of RAM is the minimum for After effects, with 64 reccommended. it's supr inefficient with RAM and plays back super slow. As well, it doesn't use GPU for most everything, and a few provesses take longer just sending and waiting to recieve data from the GPU, so you might be better off disabling GPU acceleration altogether. 
sadly, AE can only put one frame on one computer core at a time. One of my friends had some luck turning off hyperthreading, as it let AE use the cores like CPU's back in 1997 so that might be worth a shot too.

if you wanna use AE on a lighter computer like yours ()