I have the AFS 300 F4 lens which I love, but I am wanting a bit more reach for a interest in shooting the local birds. I shoot with a friend who has a Tamron 150-600 and seems to do real well with it. Just wondering what others experience has been using the TC 14 II teleconverter . I really don't have the where with all to buy a new lens right now so am wondering if this might be a viable option? I am shooting with a D7000.