Try the Apogee Wyde Eye digital cable(see Audioreview.com and Stereophile recommended components). You can pick it up at Guitar Center, and a 0.5m cable will only set you back about $35(although a 1.0m digital cable is better in theory). Apogee uses true 75 ohm connectors and I found a significant improvement over the "consumer grade" cables you mentioned. Very detailed, not bright, with a voluminous soundstage. This might be the most inexpensive way to see how much difference a more expensive cable might make in your system, and you can always return it. Just make sure you pay attention to the directionality of this or any digital cable you try. Best of luck.
Tim
Tim