This is not a complete answer. But here it goes a generic one.
1) Memory matters. So look for at least 8Gb.
2) Probably the safest bet in brute force processor now is i7. Look for the biggest number of the series. For example a i7 3xxx is third generation. A 4xxx is fourth and so on. The newer the better and cooler working environment.
Some process use several cores, no all of them. Just things like filters and renders.
3) But some processes now are done with the GPU not CPU so look for a good graphic card. There are some 3D rendering processes optimized for CUDA, which is a Nvidia software, so I would stay on that brand. A good GeForce will do.
4) Do not underestimate a good monitor... a big one is better, I like using 23-24 inches diagonal. 32 is too much for me.
5) Save some bucks to buy one monitor calibrating hardware, like Colourmunki. http://www.colormunki.com/
6) A good motherboard is necessary. This point is probably the trickiest, because one change in a component can make a difference in performance. You need one that is optimized for the processor you need, and have enough expansion slots to upgrade later.