Blubrry PowerPress includes the same category podcast feeds option as you're accustomed to in PodPress. By default the feature is not visible in order to keep the options displayed to a minimum. When you enable PowerPress and go to the settings page, browse to the bottom to the section titled 'Advanced Options'. Make sure you have 'Category Casting' checked and then click 'Save Changes'. You will then see a new tab in the left menu navigation under PowerPress titled 'Category Casting'. You can click into this area to add podcasting support to your Category feeds.
Not only can you create custom Category feeds as you are doing now, but in PowerPress you can create custom Podcast Channels. Channels are useful if you want to distribute both an audio and video version of your podcast. The Custom Podcast Channels can be enabled in the same way as the Category Casting. Also, if you have permalinks enabled, your custom podcast channel feed will look very clean. (e.g. http://www.example.com/feed/podcast/ or http://www.example.com/feed/video/)
If you want more immediate responses to questions on PowerPress, please visit our forum at http://forum.blubrry.com/ or visit our documentation site at http://help.blubrry.com/blubrry-powerpress/.