Hart - I think it would be a bad idea to go for the spun content. Here's why:
Google Panda penalises sites based on user metrics - primarily a high exit rate, presumably combined with another search for a similar term or a click on a different link in googles search results telling google that the site was crap.
If you put spun content on your pages your exit rates will be extremely high and you will be hit by the Panda algorithm (once your traffic gets above a certain amount so they can actually measure the user-metrics).
re: 'duplicate content' there is a common misconception about the duplicate content penalties that exist with google - it's not really true in the sense you're thinking. Duplicate content in google terms refers to the case where you have two very similar pages with duplicate content on your own site.
This 'duplicate content' penalty exists because in the past it was possible to artificially lift your page rank value by creating thousands of identical pages - each page contributed 1 point to your page rank value (plus extra points for any links to that page).
In this way, sites were able to create 1000 pages all pointing at 1 other page to give that other page a page-rank of 1001. The duplicate content system now distributes the page rank value of 1 equally amongst all the duplicate pages on your own site - e.g. in this case, each of the 1000 pages gets a page rank of 1/1000th. This means the target page has a pagerank of 2.
In practice, the numbers are a little different but you should get the idea.
The real point with Google and thin affiliate sites all boils down to user-metrics. If the user experience is fantastic and you have content copied from elsewhere the fact that your user experience is fantastic and users are staying will instruct google that you are the authority for this information - even if you did not write it originally.