My system came with a 2TB HDD drive. I am only using 120GB on it. I want to buy a 500GB SSD to replace this with.
For an Aurora-R7 you have the option to go with a M.2/PCIe/NVMe SSD instead . It's even faster but maybe more expensive than a 2.5inch SATA SSD, and a maybe a little trickier to get working.
Ballpark read Speeds:
Spinning HDD: 100
2.5inch SATA-3/600 SSD: 500
M.2/PCIe/NVMe SSD: 3000
If you have a question, feel free to ask, but it might be quicker to consult the documentation, forums, or tech-support for the Cloning/Imaging software you are using.