agora vs oscommerce for downloadable products

I have only non-tangible downloadable products (about 100 in total)
and I am looking for the least time consuming way to set up a store
where I can sell these to users.

currently I use amember, where a user clicks on the product he wants,
goes to checkout, pays the third party processor (which is stormpay),
once verified the processor sends a secure key back to the server to
show that the user has payed for that product, amember then allows
access to that product only for that user.

Is this possible with Agora or OS commerce? also it must work with
STormpay.

I am in the midst of getting a new host, and figure during this time
maybe I will try another shopping cart system

thanks