I would suggest to start low and aim higher. For a Production kind of environment, ideal hardware specs would be - 8 core, 64G RAM and high speed SSD for storage. Once the installation is done, try tuning the individual processes like data server, cache server, etc. If you think you are going deal with extracts, try adding another node where you can have your backgrounders run, so that your all extract data load will be taken care by 2 node.
Blogs which can help you in analyzing the performance.
Hope it helps