What's the best replacement for e-junkie / shopping cart?

I've used e-junkie to sell digital products for 10 years. It always works well and is cheap. But the UI isn't great; it doesn't look pretty. Anyone have suggestions for a replacement that feels more modern?

My needs are simple: I want a way to let people buy what I'm selling and deliver a simple file. I also need affiliate capabilities: lots of affiliates sign up to sell our products, so I want them to be able to do that easily, and for us to be able to easily see how much each affiliate partner has sold. Ideas? Thanks for your help!