Why is the performance in AE so Bad?
Please describe what you mean by "bad": it's not a very descriptive term. It could mean "slow", "pixelated", "off speed"... any number of things.
While it's helpful to list what you listed about your machine, it's even more helpful for diagnostic purposes to asnswer the questions you'll find here:
Based on your system description, you might want to consider moving OS & applications to a hard drive, and using the SSD for the AE cache. AE uses the cache to speed up certain unchanging portions of an AE comp when RAM Previewing, and SSD's are much faster than hard drives.
First, it's important to realize that the GPU does very little for After Effects, with only one feature taking much advantage of certain Nvidia GPUs:
See this page for resources about making After Effects work faster: http://adobe.ly/eV2zE7
Sorry for unuseful terms an my english
bad meens: I used to work with an old mac pro 2008, 6gb RAM, dual quad core (8cores) and a normal HD (SATA), nvidia gforec 8800 and after effects cs6. now i work with Mac Pro 5.1, Dual 2.4GHZ 6 Core (12Core), 32GB Ram, a SSD (System and Apps on it), 2xati radfeon 5770 and after effects cs6.
when work on a old composition of mine (3510x940pixel, 2x 3D layers and 1x layer with trapcode particular) my viewport by scrubbing threw in half resolution is painful slow on my new mac in compare to my old one. Conclusion: my old mac was faster than my new one;((((( i can not belive this. whats wrong?