This isn't acceptable behavior at all. By the way, I don't think you should get him DSi or PSP...I know a lot about these video games, they are way too high-tech for him. Besides, you don't want him to become spoiled from getting him all this stuff.. They are for 12 yr olds & older. Seriously, he could access the internet with those and do all kinds of cCrap with them. Well, anyway, I think that you should take away the electronics until he starts to behave better. No exceptions. If he throws a fit, throw him into the garage or something or just ignore him, keep your other kids away from him throughout the process. He will get tired eventually and stop. Don't give him attention, that's rewarding him for the behavior. If he starts to behave better, then allow him to play his video games. If he starts this bad behavior again, repeat the process I explained before and take away the video game privileges.
Your son will change to the extent that you can change how you are managing his behavior. He can earn his electronic devices (video games, computer) each day by complying with the household rules. If he violates the rules he should forfeit the electronics for the following day. And this includes stopping when he is told to stop, along with refraining from making a scene when he is told to stop. He will learn that the only way to gain access to the things he favors is by cooperating with your rules and directions. Be sure to be very consistent about this - no exceptions.