You could import the feeds into a database, then run a script that looks for similarities between product names. All the possible matches would then be displayed on screen for an operator to whizz through and say yes/no to a match. If it is the same product then mark them as the same in your database. Finally you can export your clean feed into your live database and do whatever you want with the matched products on your live site.
When you get to trust your system you could set some products to auto match based on the 'score' they get.