As there seem to be a lot of adult sites using D. It might be interesting to have a look at pay.nl and multisafepay.com.
They are 2 dutch companies which offer bank, credit/debit card, wallet and telephone payment options in a package of your choice.
All at very affordable prices. They will also help you with the scripts.

A telephone payment system is a must for every adult site as it almost impossible for someone to reverse their payments, contrary to credit/debit cards.

Anyway I think see more that you should at least have a look at it because of the mobile industry becoming more and more important.