Just thinking of upgrading for something with a bit more omph and theres only so far you can upgrade this Computer

Answer:
A base unit usaully comprises of just the pc tower with pre-installed operating system and any software the package offers.

basically a pc without the monitor, keyboard or mouse. Even though some places throw the keyboard and mouse in for free.

Answer:
a base unit is the computer tower/desktop box. It requires a mouse, keyboard and monitor to work as a full Computer