Setup Help with new Denon Receiver

Yesterday I bought a Samsung HL-S5687W, along with a Denon 2307 Receiver and Klipsch F-1 surround sound system w/ 10" Klipsch Sub.

I have a couple of questions that I am stuck on with set-up...

First, here are the following components I am also trying to connect:

1. Comcast Motorola DCT5100 HD DVR Cable Box
2. Xbox 360

And I am having a problem connecting these to the Denon receiver and getting the signal to show up on the TV.. by the way, I am connecting the Receiver to the TV with a HDMI cable. It's my understanding that with the TV and Receiver I have all I need is one cable (HDMI) going from the receiver to the TV, is that correct?

So since I am not getting a signal for the Xbox or Cable Box I'm thinking I plugged it in wrong to the receiver. Here's a picture of the back of the Denon.. can someone PLEASE tell me where I should be connecting these up to? BTW, I am using an fiber optical audio cable to connect the Comcast box to the Receiver, and I am getting the audio fine. I had to connect the cable box directly into the TV though before I could get a picture. Thanks so much in advance, this has been absolutely driving me crazy.

See the Coax connection in the top left corner? Is that where I should be connecting the Comcast box into?

Thanks a lot for the repliles! As soon as I read what you guys said it clicked in my head.. I hadn't even thought about doing the Components from the cable box for soem reason. I'm such a noob.. but thanks! I got the cable and the 360 hooked up through the Denon receiver!