Well heres the summary, you NEED a quad core, anything more is overkill.
Don't spend more than $200 on the CPU.
No more than 8 GB of ram if its for games. Two 4 GB sticks is fine. Speed doesnt matter.
Look to spend $300 on the GPU if you want to do fairly well on most modern games.
Everything else is preference.
Like AMD or Intel.
Or AMD or Nvidia.
Does it matter?
Not really.