The links are helpful but here's a little hint on how to reconcile all those manuals.
First off, get to know and love your receiver manual. That's where all your toys will be routed to and from. Once you have this idea firmly entrenched in your head. I doubt you had a problem hooking up the speakers. These arethe simplist and most direct connection back ther aside from the FM antenna.
Use your other manuals (DVD player, Cable Box, etc...) only to identify the needed outputs and how to make sure they are activated and then plug them into the corect jacks on the receiver.
Remember, simply plugging something into the receiver is no guarantee you're done. You maty need to "tell" the receiver that a certain input is hooked up and what type of signal it's looking for. Again, RTFM on the receiver.
Actually, as far as a DVD player goes, there's only one video signal (S-video, Component or whatever) and a digital audio link and once you know where to plug these into your receiver, you are mostly home. You mat or may not need to select between bitstream and PDC but ypur DVD manual will tell you this.
Additionally, you may choose to connect up a red/white analog interconnect from your DVD player to an analog input on your receiver so you can play CD's with a minimum of effort.
I assume you got the TV hooked up ok, right? I take it you somehow have the cable box hooked up to the receiver and then to the TV? ...and it's working, right? Good! there is NO standard cable box in this world. They all have their little quirks.
Sometimes cable systems introduce interference due to grounding issues. Ifthat noise goes away when you disconnect the cable, you'll need an isolater. If that's the case, ask another question or search the archives.
As far as that "TV mode" or whateveryou called it working only with thecenter speaker, well, that sounds like what DPL will do on a mono signal. A mono signal will come out of only the front centerspeaker.