I am having issues with my 13 year old daughter. Sort of like you're dealing with in regards to your son.
Currently they are in Alaska on a visit to family. All her and her older sister do is fight, verbally.
Like you I've taken stuff away, grounded blah blah. You know the routine :)
I was thiking today that both seem to take things for granted. They have been allowed 1 hour on the internet a day. Well, I know they both love the internet so what better weapon for me?
I've decided when they get back that they'll have to earn their internet time. They'll be allowed to check their emails but aside from that they get no internet time UNLESS they don't back talk, don't fight, don't argue, no name calling, do their chores etc. They can earn 10 minutes - not to exceed 60 minutes. Also, I've decided that if they earn time then do something bafoonish I'll deduct time.
Perhaps something like that will work with your son? Maybe with tv or whatever he REALLY enjoys?