If you want something fast, use an ssd. They are relatively cheap and run 10x faster than a normal harddrive. Also, Minecraft can run on a toaster, so to speak, so if you are planning on making a fast mc machine, you don't need to go all out. A dual or quad core processor will work, 8gb ram is plenty, 500 gb ssd is great, a cool case, and fans and you are set.