Shielded vs Unshielded and <$500 interconnects

Hi All,
I am keen to get a good quality interconnect to go with a new purchase.

It would appear you have a choice of shielded vs Unshielded cables. In what instance would you choose an Unshielded cable and what would be the advantages?

Also keen for your experience and reccomendations on top quality RCA cables maxing our at $500? I currently use Chord Cobra and Chamelons.

Cheers
N