Actually, you've got things a little mixed up.
E-junkie is a shopping cart and delivery system for digital goods, while 2Checkout is actually a third-party payment processor.
If you use E-junkie, you have to still use your own Paypal account to accept payments. But with 2Checkout, they process the payments on your behalf and then pay you out for your sales (minus their commission) directly.
~blackhatdiva~