You need to post this on the other side to get help.

I have only one Monster Cable product, which I bought cheap at Goodwill. It's the cable from my DVD player to my receiver. I can't honestly say it sounds any different from the vendor-supplied cable that came with the DVD player. It simply was long enough to reach what it had to; the original one was not. There is an entire "cult" based around the qualities of various cables and their materials and construction, and the sky is the limit on what some people are willing to pay for them. While there may be discernible differences between cables, IMHO they are just that -- differences -- not necessarily improvements. I would venture that most folks out there would not experience any kind of improvement in using fancier cables -- certainly not while the cable company signal and room configuration has such a great effect on what you actually see and hear.

DVI to HDMI adaptors work fine. However, you may not notice any picture quality upgrade moving from component to DVI. Like component cable hookups, DVI is video only so you will still need audio cables connected.

How many you need depends on how you want to hook it up. I have an SXRD also, and it has several HDMI inputs. You could connect your DVD player and your HD-DVR directly to the SXRD using 2 of the HDMI cables. I have tried both the composite and HDMI inputs and can't tell any difference in picture quality. What I have noticed is that the HDMI "handshake" takes longer on the HDMI inputs when switching to them. The composite inputs don't have this issue. I don't see any particular advantage in running the HDMI inputs through the Onkyo, unless you have more HDMI devices than HDMI jacks on the TV. My Onkyo only switches two HDMI inputs. It has I think 4 or 5 component inputs.