Best paying PPV ad network?

I'm looking for best-paying pop-under (or any other ad type, whatever pays the most) on CPM/PPV or whatever you call it, bases. I'm currently running Clicksor, but it doesn't work very well, I don't want to get into details.
Mostly I get traffic from Latvia, US, UK and India (In that order) so basically I need ad network with ads for every country.
How much CPM can I expect from this traffic? Which ad network do you recommend?

Don't have a specific recommendation for you, but a suggestion: Why not try finding you own offers and finding them? Use OfferVault or another similar tool to find offers related to your website. Most information products are global, including in Latvia. You'll probably make more money this way than by placing popunder ads. Unless you have major traffic, you'll just be getting Run of Network ad buys which are very untargeted, meaning you get a very low CPM unless someone directly targets your site. So you'd make a higher CPM by highly targeting your own offers for your own site instead.