Special digital cable needed?


I just bougth a secondhand Yamaha DSP-E800 DD/DTS/Prologic decoder with built-in amps for centre and rear speakers. So I wanted to hook up my DVD-player, using a 75-ohm cable to feed the digital input on the Yamaha. Since the shop didn't have a digital cable and I didn't want to wait to play with my new toy, I just used an old analogue cable. And it works. And it sounds pretty good too. So my question is: will replacing this cable with a 75 ohm digital cable sound better? Or can I save the money and waste it on other joys of life?
satch
Thanks for the responses, untill funds allow I just use the old analogue cable. Audioengr, just one question: why a minimum of 1.5 meter? With analogue cable should be as short as possible, and 0.5 meter would be sufficient.
Satch - this article I wrote for Positive-feedback explains it:
http://www.positive-feedback.com/Issue14/spdif.htm
Thanx Steve, I read it and almost understood it - just let it digest for the night and I will be OK. Just for the record: I can lend a digital cable next week, and plug it in. I keep whatever sounds best......