strykeroz:
As a rule should you wire GND to a metal enclosure, or should that be avoided, or doesn't that matter?
Actually its quite complicated - you want to avoid (signal) ground loops, yet you may need to (mains) earth metal enclosures. In general signal ground and mains earth should be separate (except at maybe one point) Using chokes you can connect grounds at DC but effectively separate them at signal frequencies. The main issue is ground loop currents flowing along the shields of screened cables between enclosures - the IR voltages then add to signal voltages typically leading to strong mains hum.
If the signals aren't low-level audio it will matter less, typically RF signals have case ground the same as signal ground for instance. Logic levels have a volt or so of noise immunity so its less of an issue unless a very electrically noisy environment (lots of big motors in a factory).