Welcome, Paul. The 14ga Parts Express cable would be plenty for 30 feet in-wall. You could pay a lot more but you wouldn't get anything significantly better. One thing I'm curious about is the 30 foot in-wall runs. Couldn't the 3803 be placed close to the front speakers and TV for a short direct run?

An example of a 25 foot component TV cable that would be fine is this . If 30 feet is necessary, it would run a fair amount more, since that isn't a standard length(I'd have a different suggestion).

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Enjoy the music, not the equipment.