Just purchased the Logitech c920 webcam. However....

I just bought the Logitech c920. It works beautifully.

However, it has a nasty habit about defaulting back to the webcam's built-in microphone, which sounds absolutely horrible... :-(

I have a Samson C03U USB multi-pattern condenser microphone that sounds amazing, but the Logitech software constantly reverts back to the webcam mic. I disabled the webcam mic in the computer's sound settings, and this seems to have remedied the situation.

Has anyone else had this problem?
I was also wondering if anyone knew of any sort of cool enhancement for a basic webcam setup. I have 4 60 watt bulbs (one near each corner of the screen). I also have a black backdrop and a Samson USB condenser mic.

Am I missing anything important? I think I have the basics covered. All I need is the ability to get a good headshot, so I can video chat.

Any ideas?