You don't need that much storage, instead bump up the RAM to ECC and get a motherboard that supports ECC RAM. One SSD will suffice fine. It won't really be the server that is the bottleneck - more so your internet connection - are you sure it'll be able to handle 2000 people pinging it repeatedly? Is your internet connection basically DDoS proof? Also, what is the upload speed of it - will it be able to handle transmitting a large minecraft world quickly enough over the internet?