Sonar Contacts

[DigitalAura]

I know RR would likely disagree, but I am of the opinion that the most valuable asset on the sub is the sonar gear, esp. passive.
It's value is a combination of its usability, reliability/accuracy and its worth in being undectable as it is being used, unlike radar or asdic.
You can get on without radar, but not without sonar (at least, you can operate covertly with sonar and continue to do damage).
That said, I think you've hit upon an important element to the sim. That is, YOU should be the instigator, YOU should be the best crew member, YOU should be the driving force behind what happens. If the crew can do something BETTER than you can, then it removes any impetus to man that station. It takes away from the immersiveness of play. It discourages a player from taking part in that element of gameplay.
If you can hear further and better than even your best sonar man, then it provides YOU with a richer experience by ensuring that you will be more attentive at that station.