I've never posted in this circle before, but have come here occasionally. Let me say that I enjoy the Tone e-Zine and think the articles are helpful and informative, ad copy and photos first rate.
I think it's helpful to have your own circle just so you can set the Tone (pun intended) of your communications as you are the originator of most of the posts in your circle after all. But only you can answer whether the overhead in money and time is worth what you get out of it in increased knowledge, better product awareness, fun, or whatever else floats your boat.
So I think it's good to have an outlet for informal communications. Then the question might be is it best accomplished here, or on your own website? This would be ala Stereophile Magazine that started their own audio forums a few years ago, or Positive-Feedback that has their own letters to the editor feature.
You say your goals are to be more of a resource and how you can be more "worth it" to us. Those are tough questions, so this will be an incomplete answer as I've only given it a little thought.
First, I think you should include a link to your AC circle from your website, and encourage a "talk to the editor" or "talk to the columnist" approach. Second, downloading an entire issue and grasping all of that can be a bit daunting in an online environment. I'm 48 years old, and I still prefer printed material. I know you're not going print, but perhaps organizing your website a bit more like Positive-Feedback so you can view tables of content and focus in on your specific interests might be more user friendly and generate more user interaction and interest. Then you could start threads here and point to specific articles in your e-Zine for further discussion.
Those are just a few thoughts and I'll come back with more if I think of any.