[tonyvdb]

The receiver must support DTS processing (Digital Theater Sound) or it will not function. Does the receiver clearly state on the front that is processes DTS? It will have a small DTS logo somewhere on the front.
DTS has a slightly higher bitrate and thus usually will have more dynamics and can have as many as 6.1 channel sound not just 5.1

 

[tonyvdb]

It says Dobly Digital. No dts in sight I'm afraid.

Ok then you wont be able to use the DTS audio from the DVD player just use Dolby digital, very little difference.

I have it connected with the coax cable that came with it, but it looks an awfully lot like a normal video rca cable, yellow instead of orange as the jacks are.

Yup, thats what it is and it will work just fine as its a digital signal and is not subject to interference like analog.