Recommend an online-shop software for digital content?

Hi there,

we have just started a project about building up a large online shop for digital content.

We have evaluated OSCommerce and Zencart and we are not 100% content with any of them.

For our shop the customer will buy digital files with a usage license. We can live with the fact that we probably need to make a seperate package for every different license of the same product, although the main product file is the same.

What we really have a problem with are the file sizes. With files of sometimes several gigabytes http upload is a no-go, so we want to ftp them to the webserver and then integrate them into the shop. An important thought here was protection of the file, we would like that only logged in users can access and download the file and preferrably also for a limited time (like 3 times). Partly we were able to do this with oscommerce, but we really want to be sure the link is protected, as some malicious user spreading a link could easily attract enough illegal downloaders that draw terrabytes of traffic. Due to our policy we can not and will not digitally protect our content. However, we would like the system to automatically produce license Jpeg images, that look like a seal and have the name of the licensee on it. We think this is not possible without root access and installing some image processing module similar like ffmpeg or so as native php does not seem to enable us to manipulate images like that. SO the idea would be that it could work with Flash/Java? Is there something like this available?

Even if you can not answer the above questions i think maybe a recommendation of a general online-shop software that is heavily focused on digital (downloadable) products would help. Or maybe addons for zencart/Oscemmerce/etc. We are looking preferrably for free/open source solutions as we need to customize a lot and already are on a quite tight budget here.