I just got an old/used woofer to go with my ~$400 Denon 7.1 A/V Receiver. I have a bunch of old RCA cables laying around (Very thin wires), will using half of one of those work...or do I need to buy a ~$10 Dual Shielded Subwoofer Gold Plated Pro Grade blah blah blah cable?
Any RCA-to-RCA cable should work just fine, but if you notice interference, then you may want to buy a cable like this one from Monoprice
Thanks! On a tangent, is it recommended to change my front speakers to SMALL in my A/V receivers option so more frequencies go through the woofer?
... is it recommended to change my front speakers to SMALL ...
Generally speaking, yes, you should set all your speakers to SMALL and let your subwoofer handle the lower frequencies.
Your Denon AVR comes equipped with Audyssey - here's what they have to say