According to the rumors, the cheapest one will use a Qualcomm Snapdragon 652 processor, 3 GB RAM, and 16 GB internal storage, while the top-of-the-line will pack 4 GB RAM, 128 GB storage, and a Qualcomm Snapdragon 820 SoC.
http://www.notebookcheck.net/HTC-10-to-come-in-three-variants.161691.0.html