I'm using Powerstore 2, not E-Cart. But to answer your question, I have Ecart 4.5 installed.
The Paypal checkout is the normal button that comes built-in.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.