Things to consider…

>>> Connectivity

Almost all the models take sound out of your Mac using a 3.5mm jack lead but some also include USB or Bluetooth. A number also feature RCA inputs for connecting CD players and turntables.

>>> Power

Generally speaking, larger speakers have a higher power rating and are capable of greater volume than smaller ones.

>>> Fidelity

Some of the more expensive models on test are suitable for more professional uses like music production, where greater precision is required. Is this something you might want to do in future?

>>> Portability

The smaller models are relatively portable, whereas the larger models are designed to remain firmly on the desktop.