Power store is intended to be a Ready Made application that was created using WebAssist Extensions. It is intended to be used out of the box with the advertised payment gateways. The feature list advertise Authorize.net payment gateway and PayPal Payments Pro gateway. The included features are listed on the Feature list.
If you need features that are not built into PowerStore, than you can use the WebAssist Extensions to modify Power Store to add that functionality. As with anything however, there are going to be limits to this.
The issue with inventory control and Paypal Payments standard is in the way Paypal payments standard works. When using PayPal Payments standard, once the user goes through and they reach the checkout success page, you really don't know yet if transaction has gone through. It only means paypal has excepted the payment details and have placed the transaction into a queue. Once PayPal does make the transaction, they issue an IPN post containing the success or failure messages and other transaction details.
PayPal Payments standard requires a completely different workflow then PayPal Payments Pro.
The Power Store is a fairly new product that was created for users who do not want to bother with eCart, they just want a store up and running. Version 1 only supported Paypal Payments pro and USPS. In Version 2 we added more shipping providers and Authorize.net. When we release version 3, we may add Paypal Payments Standard, however at this time, it is not supported.
As for you comments about iRite, what we are selling is the integration of FCKEditor into Dreamweaver. Rather than manually downloading the FCKEditor and configuring it on your page, the iRite Extension adds the FCKEditor to your page for you. We are not selling the FCKEditor, we are selling the graphical interface that is used to configure the FCKEditor.