i wouldn't sell a niche site first to an unfiltered surfer looking for "porn", no matter how good it is. of course most surfers have some fetish, but they're all different. so i try to sell them a general option first that suits all tastes, like the large movie sites. i have tried the networks too, but the ones you mention except brainpass are totally oversaturated imho (especially brazzers which you find on most large mgp's and on every tube site).
what porndragon mentioned, selling free porn memberships to the freeloaders also works well...then filter them and sell the niche sites
