You can indeed use a standard IDE cable in place of the proprietry one, the only difference being that the one creative uses has a few holes in the connectors blocked out, so you cant use their cable as an IDE one. Simple as that.
Rounded cables shouldnt pose any problem, but weirder things have happened. I actually rounded the cable between my Audigy 2 and the bay myself, and it worked fine. My advice is to try it, if it works, then great. If not, use a normal IDE cable, or the one that came with the card.