In order for you to play X3: Reunion on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
10.7 (Lion)
Processor (CPU):
Pentium® IV or AMD® equivalent at 2.0 GHz
Memory (RAM):
1 GB RAM
Graphics Card:
256MB OpenGL 2.0+ discrete NVIDIA/AMD card or Intel Core i7-2620M
Hard Drive:
5 GB of free space
In order to play X3: Reunion on macOS with maximum graphics settings, you need a computer with a configuration no worse than the following
Operating System:
10.8 (Mountain Lion)
Processor (CPU):
Intel® Core™ 2 Duo or AMD® equivalent at 2.0 GHz
Memory (RAM):
2 GB RAM
Graphics Card:
512MB OpenGL 3.0+ discrete NVIDIA/AMD card
Hard Drive:
5 GB of free space