My suggestion is an integrated approach.
Get one main brand name and stick with it. Produce variations of it for different themed sites. Few companies in adult do this, but the ones that do are very successful, eg, Playboy, Girls Gone Wild, etc..
It seems like most of the other companies pump and dump. They promote a site, milk it for money, and then run it into the ground. Then, they get a new site and repeat. Sure you can make money that way, but the big money is in building long term brands.
Naming is one of the main things my company does
http://namingsystems.com