These are the payment services we currently support:
http://www.e-junkie.com/ej/help.payment.processors.htm
We will add Propay to our wishlist for consideration as a possible new payment processor to support at some point in the future.
Please understand that adding support for a new payment service is not something that we can do quickly nor easily; indeed, it's one of the most difficult and time-consuming tasks we can undertake, so we have to consider whether the benefits of a prospective new payment processor would be broad enough for a wide enough number of merchants to return our considerable "investment" in time and effort required to support it.
Many payment services cannot be integrated well or even at all -- a lesson we learned with a couple payment processors where we eventually had to give up on full support and only support them with Buy Now buttons, and somewhat clumsily at that. As such, and since we already support a wide variety of payment options for US-based merchants, any new payment services we might evaluate for integration would be those with the broadest international support for merchants outside the US and with the best prospects for full integration with our cart.