Making the Webhost4life ecommerce module actually work was a bit of a pain. They have multiple versions of the same ASP file included and you have to figure out which is the latest version (not too hard). The product and order databases are stored in MS Access .mdb files so there is no modification needed to DNN...all we did was run the store inside an IFrame module, so this solution would work well with any version of DNN, including 3.0.13. For $9.95, it was a good bargain to get up and running quickly, but you need to know the older ASP model. You can run ASP.Net and older ASP applications concurrently under IIS.
Webhost4life has been a decent hosting company, with reasonable response time to any questions I've had. I have two sites hosted there with no problems and good response times, but your situation may vary. I'm going to give another hosting company a try for the next DNN site, just to see if I can do better. For $10/month, Webhost4life is a good option.
If you have good design skills, running any kind of application inside a DNN IFrame provides a number of advantages, including the option of building out support for multiple mobile devices and web services with no modification needed to DNN and no dependancies on any particular version of DNN. We like to think of DNN as an excellent visual shell around our real applications which are not dependant on DNN.
However, there are disadvantages to this approach, including the difficulty of optimization for search engines and the neccessity of using multiple databases if you don't want to be dependant on DNN. One of these days I'm going to get around to learning the DNN object model and build some modues. But, during the day I'm very busy building c++ stuff, so who knows?
If you're set on buying a module, I can recommend PortalStore. It is very robust though a bit complicated for a simple sales application if all you want to do is sell a few items, but it produces static pages that work well with the search engines. If you have a lot of stuff to sell in multiple categories then for $199 USD it is quite a bargain. We will probably move our little cart to PortalStore when I get around to it. I would have used it from the beginning but the latest version wasn't quite finished by the time I needed to have a store up and running. Richard Cox is very helpful and responsive to questions, even for DNN beginners like me.
I haven't used Catalook, but a lot of people think it is good. The sites I've seen using Catalook are below my acceptable design threshold, but I'm sure with a little effort put into the implementation it would also be a good choice.
Hope this helps,
Paul