Congratulations, that's going to be a very nice systems
I've no experience of ready made XLR cable brands - I'm sure others here will offer recommendations - but I can fully recommend using XLR over RCA interconnection even for short signal runs.
With Balanced interconnection, the audio signal is "isolated" from the Earth / Ground connection between units - this Ground connection is now only used to set the Common mode voltage between units and not directly for the audio signal.
Who ever dreamt up the idea to share the delicate Audio signal with the Ground / Earth interconnection was having a very bad day at work...