Hi Computer Candy,
I spoke with one of my co-workers who works as a full-time Magento Administrator. Basically, I asked for his opinion about using Joomla with the extension for Magento. His reply was much like Slinky's- just keep them apart. You can link into it from the Joomla side, but don't try to integrate.
You can theme your Joomla site (or your Magento site) so that they look similar, and then link into the informational side (the Joomla site) and when you're trying to sell something, then bring your customers to the Magento side of things. Additionally, remember the resources that BOTH of these solutions consume. If it's going to be a very large site, make sure that your hosting solution is up hosting it without any issues.
Hope that helps!
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