I just bought HT-S580 Onkyo. I've heard the first thing you should do is buy 16 gange speaking wiring and a decent coaxial cable. My HD Dvd doesn't have any special wiring, just what came with the TV. I don't want to spend a ton, but I want the system to sound as good as it can. None of my wiring has gold tips and I don't have an expensive surge protector. I also don't have a progressive DVD player....how much does this make a difference?
Just leave it alone. Why did you buy a fairly inexpensive home theater in a box? Probably because you wanted to save money and you don't really think that you should spend a lot of money on this things, right? Continue saving your money and leave it alone. You will not hear any considerable improvement in sound by doing what you plan on doing. If you want improvement, expect to shell out a few more coins.
The ratings on this system are amazing. The money wasn't a factor. I live in an apartment, therefore I can't play the system very loud. However, I want the sound to be as crisp and as full as possible.
You can replace the speaker wire with 14 gauge and get a well ocnstructed coaxial cable. Other than that you should be fine. If it has amazing ratings, you should not have to do anything else.
Does your TV have component video inputs? If your DVD has component video outputs use it regardless of progressive scan capability.