Can I use component video as my audio inter-connector?
any foreseeable problem or downgrading of sound if using video cable as audio cable?

Sure, why not? They're the same cable, just with different colored ends.

Even more so, video needs a bandwidth of MHz, where audio is only kHz. Cable designed for video use makes excellent audio cable.

Somehow I knew you'd be along to fill in the bit I was too lazy to type...

I use RG6 coax terminated with RCa connectors for my interconnects when I hook up the Denon to an external amp, it works very well.

I used RCA video cables in my old 5.1 analog audio setup with no issues at all.