if its an imagehosting site with large no of pageviews then go for adbrite... else adsense is the best...however depends upon the no of UV's you getting and your niche....
CPX is one of the lowest paying companies out there. Only use it as the last chain in your, meaning throw all the trashy traffic that doesn't pay to CPX. If you are going to get fair results with CPX, you have to use it for your poor international traffic because CPX at least pays you even for international traffic. Trust me, it's a known fact CPX should not be anyone's main source of revenue on there web site.