In order for you to benefit from Multiprocessors with amd or intel or Sun. You have to have the Multithreaded application to take advantage of it. Such as 3D studio Max, Truespace, Data Base applications,GoGo MP3, Video Editing and etc(please don't tell me Quake3 and Photoshop because q3 is poorly written for Multithreads and Uniprocessor for PS will get you by now adays even with large filters).
Most of the time you see ppl in a forum discuss how Multiprocessor system they have "is so repsonive" when they are burning CD's and browsing the web and watching dvd's @ the same time.(don't ask me why they do, they just post it up everytime). The reason why you didn't see any benefit from dual amd in anands benchmark is because most of the time those benchies are synthetic and non multithreaded and don't paint a real world picture of the performance. I think that was one of anands points he was trying to make in that overview.
Multiprocessor systems are not mean't for speed but they are viable means for task that require such power and balance.
For Example: Joe Blow wants to get from point A to point B everyday for work. Joe can get from A to B with an Average size car such as a Yugo. But if joe has 100 boxes that need to be shipped from point A to B in a small amount of time then Joe is going to neeed a Truck. So Instead of joe moving 2 boxes in a yugo, he uses the Truck to get Twice as many boxes moved in a reasonable amount time.
Understand the concept now? You can get the work done twice as fast with dual processors when the Job(multithreaded) application calls for a dual system. If the job is written to take advantage of it then you will not see the performance increase such as in anand's review that you read.I hope i didn't throw you off anywhere.