On my Dialogue 2 use RCA to 1/8" mini (stereo). I got mine on eBay. It has gold plated connectors, good amount of length (5') and is oxygen free copper and shielded and has a nice fleixble sheathing on it. Made by Monster for about $20.
Don't spend more than that on a cable for the iPod/iPhone. You won't notice a difference as the device isn't there yet.
Be sure to keep the volume down on your iPod. The highest setting is too loud for line levels. About 2/3 the way up is decent enough.