Should I buy another hard drive?

Recently I bought an old PC to start using as a home server for storage, running a game server, etc. I bought a PC that was listed as having a 1 TB HDD, and I was expecting to just buy a 128 GB SATA SSD as a boot drive for my OS and any other critical things on.

Instead, I opened it up today and it had a 1.6 TB SSD inside of it...wtf? So now I'm considering buying an 500 GB HDD instead. Would it be worth it? Honestly, 1 TB alone is more than enough for what I have to store but I don't know if there are any other factors to consider.