Definitely depends on your traffic volume. If you can justify cutting out the middleman and sell directly to advertisers, as mentioned in the prior posts, make sure you have a quality advertising pitch displayed. This pitch should illustrate the stats of your website (UV's/month, demographic, expected growth, etc., etc.) and the ad options you currently have available.
If you still need a network, maybe try a CPA/lead-gen program that pays out substantially more. But, as these pay per lead, your traffic volume should remain high as well.