Glad you are going to give it a go! I used worsted for SSClass, with a 40" cable (I'm pretty sure, its been awhile!) and it was plenty long enough for me. I used KP washable wool, which, BTW, did felt and shrink a bit and made for tight socks. And now sadly apparently some silly M*THS got to them and they are sporting a large hole on the heel of one-aargh! Sigh...But enough of my sad tale, lol!
If you are going to use sock yarn it will make a great pair of socks, but you'll have to do some math to get the gauge right. You would need a lot more stitches per inch, and I've always heard it recommended that you need to check gauge using this same method you'll use for knitting the actual item~in this case magic loop. I apologize if I am stating the obvious, I don't know exactly how long you've been knitting so I just don't want to leave anything important out
Good luck! I'd love to see your progress once you get going!