What's the tall cabinet on the right being used for? If you're married to the current setup, your best (and easiest) placement for the sub is a bit in front of the tall cabinet. The cable won't be too conspicuous, especially if you can run it behind the cabinets into the back of the media cabinet.
I agree on avoiding wireless and would even move the R/L Fronts in out of the "corners" a bit. Depending on your sub, you'll also need a power outlet to plug it into. Good luck with whatever you decide.
"I don't think you fully understand, Bigelow... you've been murdered."