I don't know if you are willing to give recommendations for extensions, but I'd like some advice as to which extension(s) to look at. I don't have a particular project in mind, but I do want to create a demo of a newsletter/subscription that I can show to clients. I want to find a solution that I can focus on to develop hands-on experience and to offer to my clients.

What I'm looking for is a system that handles newsletters similar to iContact and Constant Contact (custom fields, segmentation, reports, subscription management). I also want a system that integrates with the content of the web site -- able to pull in the latest articles from the site. And I'd like the content to come from K2.

From what I've seen and read so far, I lean toward AcaJoom Pro/JNews. I'm looking for the best value (features and usability), and if that means a commercial product, so be it. Do you have any insights or recommendations to share?