Yeah, that article was back when AMD was better than Intel. It's a lot different now.
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3153&p=6Intel is better than AMD. =/
I would easily go for a quad core if you're looking to upgrade now. It's going to cost you a little bit more, but you won't be having to upgrade for a few years. Since you say you're pretty hardcore, I would definately recommend it. As long as you upgrade to a dual core though, you should be fine.
The biggest performance boost is still going to be the graphics card though.