Hi ifwearner it depends what you want billing for, VISA only allow certain niches to be billed anything dodgy the main processors wont touch at all.
Try ccbill (.) com or epoch (.) com or as already mentioned verotel (.) com (sorry for the brackets its not allowing me to post urls yet ive not made 15 posts)
I would suggest ccbill however espcially if you are wanting to pick up affialites as they have the biggest affilaite userbase already so getting them to signup with you shouldn't be too difficult if your product is decent.They also handle payouts to your affiliates which are always on time and takes that headache away from you. The only drawback is the charges if you are not doing big money then they take 16% and a rolling reserve for 6 months.
I then 2nd epoch as they have a very similar structure to ccbill and affiliate system, they also handle payouts and have a very similar charges 14% when I last checked.
I haven't personally used Verotel but they're a long established company with a good system I also think they bill for some of the slightly more dodgy niches.
As far as an adult cms goes ive used many and many are not upto the job, I currently useelevatedx.com on all of my paysites its got to be the best on the market and if you dont have a spare $5k for the full script they have a $150/month deal.
I hope that info is helpful and PM me if you need any exra pointers.