There are a few differences between the two models but the main ones are:
76 has 8MB of memory, 4 level grey LCD, 125 waypoints and 16 HR battery life
76C has 115MB of mem, 256 color, 250 waypoints and 30 HR battery life
I have checked all the websites you have suggested and still find that deepblueelectronics.com is untouchable by at least $15 -$20. I never heard of them before so I am a little hesitant about buying through them.