No barking? Some barking?

[katdog5911]

I have been working on Stella's yard barking the past few weeks. I confess I got a bit distracted over the holidays so I think I will just have to start over again. My trainer ordered an e collar for Stella to help with training.
My question is how much barking is ok. My dh feels I am over doing the no barking in the yard. And honestly, I do want her to bark when it is appropriate. But not sure when that would be. I know I do NOT want her barking at the cat across the street, that just loves to sit where Stella can see it and just hang out...lol. And I do NOT want her barking at the little fluffy dog across the street and I would love for her to stop the frenzied barking at the 2 dogs a few houses away. (both of which get out of their yard and wander into mine sometimes, and one of which charged at Stella in MY YARD!) I can understand why she is barking at them, but enough is enough! Will she be able to understand that it is ok to bark sometimes and at certain things? And the trainer said I should use the "C" on the e collar at a low setting, not the "N". Any thoughts?