Oh, trust me, I've tried all the major networks, along with every network dedicated to my niche, but they were all far worse, in both earnings and ad quality. There's a reason almost everyone is using AdSense when they're not selling ads direct.

there is a significant gap in typical earnings between adsense and a highly optimized display service.

the only way to bridge that gap really is expertise or consulting, typical website owners will have neither unless they are very large (think alexa top 1000).