Justin,
First, let me assure you that what you're going through every other user on this portal has gone through, or something similar. I wish I could say I have a good suggestion, but I have seen sales, (not just Jr. sales either) to similar things or even create duplicate organizations. And as far as I know, there's no way to limit those imports in SFDC.
I like Jeff's solution, and I will check out DupeCatcher