My oldest etched her name into the side of my minivan when she was about 4 1/2 w/ the end of a sharp metal stick & claimed her 18 month old sister did it! Talk about feeling the love! I certainly feel your pain. I'd agree w/ Love & Logic.
Also, just started watching Super Nanny the last month or so- what a neat lady she is! She has dealt w/ many kids w/ behavior like your son's. It was rough! But persistence seemed to be the key- & sometimes enforcing consequences- like sitting on the "naughty spot" (time out) would take hours. Each time the kid got off, the mom had to but him back on until he stayed & apologized for his agression or whatever...but it eventually started to work, once the kid figured out mom wasn't giving in. The keys were remaining unemotional & NOT speaking AT ALL to the child when he got off & had to be put back on & being persistent. They are, we have to be, too.
I think, too, you have to find out what really hurts when it's gone. He may not care about somethings you took away, but there's something there he's not wanting to lose. You could always try upping the ante & make him go give the toy, etc. to Goodwill, if it's not earned back within a certain space of time. Have you tried taking away the TV?
I know these are trying times. My oldest, as bright & responsible as she is, is also very dramatic, persistent and overly sensitive. You try counting to a time out 1-2-3 she blows a gasket at you on 2. Whereas my youngest will usually give in at 1. We've just made it very clear, she can blow all she wants, we still love you, but your behaviour gets you nowhere. We DO NOT give in to fits, tantrums or rages. The positive is, she has gotten MUCH better & easier to deal with at 8...time & age maturity can help- but it ain't fun wating for the maturation process. Love & Logic does have some great strategies for dealing w/ these issues. Check it out!
D.