I have always felt that you should offer all the content on the site for free and support it with ads. Then offer subscriptions to those who don't want to see ads. Subscriptions kind of cheapen the experience for me. Particularly when I see posts promoted to the homepage from the subscribers forum and they are worded to try and entice us to subscribe to read the "meaty" content. Sometimes it is pretty obvious and makes me not want to participate on the site that day... since I feel you are trying to dupe me into a subscription.
I know, harsh, just how I feel sometimes.
Just being honest, I think there are good advertising options for your brand. I think you could do very well in direct sales advertising. You are so well known to so many targeted companies I would think you could name your price and keep it very clean and reputable.