If you are wanting to upgrade a whole new system, there has never been a better time to wait than now. I would buy some of the components slowly...ones you know that will not become obsolete. AMD's are great in gaming right now, but that is soon about to change. The word is "Yonah"...do a search for it here, and on the Internet. Do much studying on it, and you will see huge performance increases coming. There are some Dothan's right now that are just as strong as the AMD's, but the new Yonah's are going to be the biggest step Intel has made in a long time.
On the apps you are going to use right now, you will never see an increase in performance using either Intel or AMD as none of them take full advanatage of the CPU anyway. You will see an increase in performance with video on an Intel though as many have stated. On gaming it's a wash. On benchmarking AMD's lead the way at present, but as stated that is about to change. The sythetic benchmarks are a measure of full @$$ bore preformance though, and you will not see that in games. I can run PK, Doom3, and many simulators and racing games on my current Intel machine without missing a single beat. These are very dynamic high speed games.
If you are familiar with Intel stick with it. AMD's are very different, and they do have little quirks you have to be aware of to get everything to run smoothly. An Intel will run smooth right out of the box. Me and my freind are all the time comparing our systems and his is an AMD high end gaming system. The only thing drastically different is that my Intel encodes much faster. His is a little faster at benchmarking, but other than that you cannot tell a difference in actual use.