HP Quad Core-12GB-2TB

The difference is speed. A 2 TB drive is really, really slow.
BUT, there is hope, you can fix that.
The operating system should be installed on a small fast drive. (like 70 GB, example)
The 2 TB drive is used to store files, such as, pictures, documents, music, video...
But, do not mix the operating system with all those files. Keep them on separate drives.
Set the bios to boot the small OS drive first.
Now the system will go way faster...

what system? all you said is that it will be a HP quad core, that doesn't help at all.

^ and what is the intended use of the system, ie video encoding, or gaming, both??

What system(s)?
You no make any sense.