Ask HN: Payment solutions for a marketplace app?

The project I'm currently working on is a marketplace style web app, facilitating sellers to sell their products to customers though the web app, with me taking a cut in the process. I've been doing some research on possible payment solutions tailored for this type of web app, I've come up with the Amazon FPS Marketplace and not much else at this point.

Can anyone give any guidance or the benefit of their experience with what might be some good options to investigate further?

The full merchant account/payment gateway option would be my least preferred, due to the seemingly higher costs involved, but if this option has enough advantages over something like Amazon FPS or Paypal in so far as enabling the marketplace style model I'm going for in the most user friendly way, perhaps the cost might be worth it? Particularly seeing as my ideal situation would be to have something as seamless as possible, such as:

1. Buyer places order via website and pays by CC without appearing to leave website

2. Buyer's payment is transferred directly to seller's bank account, minus my cut, notifications sent out to buyer and seller etc.

It appears that using Amazon FPS or Paypal would necessarily require more screwing around for the customer/buyer than this. But the lower cost of such options is attractive on the face of it, particularly as the ticket price of the products my prospective sellers will be selling is not huge and I'm realistically not expecting an immediately massive amount of orders to be processed through my site when it first goes live.

I'm not in the US.

Any comments much appreciated.