If you're going to buy an Intel system, the "wait a little while" advice may be worth it. The Prescotts are going to be released soon with a P4-E classification compared to the P4-C of the current Northwoods. Benchmarks are showing that comparable Northwoods will outperform the Prescotts until the Prescotts are released at higher speeds.
Intel will slash prices on the Northwoods when the Prescott is released so I'd wait until that happens if you're going with an Intel system.
http://www.anandtech.com/cpu/showdoc.html?i=1956