I have a 300 watt, 100 watt RMS sub, and was wondering if I need any soecial cable, or will any rca cable do?
There are dedicated sub-woofer cables out there on the market. Ones with good protection from noise/interference will do, but really, it needs to be a good system to notice much of a difference between a $30 cable and a $100 cable.
You do not need special subwoofer cable. Hell, you can make your own. Just get some rg-6 (the ones used for satellite) 75ohm cable and terminate them with RCA jacks. They may not be very flexible, but they are surely shielded.