The add to cart code in the PowerStore is all located on the product detail pages. In here if you remove the add to cart code that is at the top of the page you will no longer be adding items to the cart when the button is pressed. The button itself is part of a form on the page, you can alter this in any way that you would like as well. It is all very straight forward php coding on this page. If you have the eCart installed you can just remove the add to cart server behavior on the page.