Those adapters just add one more connection that lower signal strength and quality, and can make for a less secure connection. I never found any high quality ones when I looked, and the ones I did end up trying were somewhat loose in the soundcard jacks.
Here's a decent one for $6, but it's 5' long. I use that one for a portable player.
NXG has several models from $3-20. I used several of the nx-0223 for a while on my carpc, no complaints. They're very flexible and of decent construction, best for the $ IMO.
Don't fall for the Monster Cable marketing, they are a total ripoff. Actually, most cables in retail stores are, that's the biggest money maker. I was just in Best Buy today, they had a special on the Monster glass optical cable, "only" $99! I couldn't believe it. The salesman was telling me how well-shielded they were so the sound would be preserved.

I could get a glass optical cable online for $35, and an expert wouldn't notice a difference on a $100k audio system. Hell, an expert probably couldn't differentiate between that and a $5 plastic cable for home audio.
I could also go on about how USB cables are all gold-plated and going for $30-40 now for 6' lengths, but I'll just say that I'm glad I make my own for more like $2.