Increasing your signal level beyond 4v probably isnt going to fix any noise problems that you have. If you believe youre going to have noise problems, consider running your signal digitally or balanced.
Ah OK, so Symbilink is just their proprietary balanced connection.
I think in general, you can probably get away with normal connections and just be smart about running them away from noisy sources. Maybe some cars are particularly noisy. Or if you have extra cash and want to not even have to deal with the possibility of the issue you just get balanced/digital hardware.
I'm guessing if you have this equipment, you already know what a balanced signal gets you, so I won't explain that.
Edit: Also, I took a quick read around the internet and they make cables to adapt Symbilink to RCA if that is something you would want to do for whatever reason.