It depends on your particular circumstances. Are you buying a new processor to go along with the new motherboard? Are you sure your motherboard supports your existing peripherals and everything you want to use it for?

i already picked out a mother board that supports p4 and celeron 1.7Ghz to 2.4GHz and all my hard drives and such plug right in.

One question will the pci slots and agp slot line up with my current tower? i have a ATX tower adn the MB is ATX.

And I found that many different companies make the same cards and put their name on it like, Visiontek Xtasy and Gigacube Radeon, well umm do you still get the same perfromance out of a gigacube Radeon 9600 pro as a ATI Radeon 9600 Pro, the gigacube box says ATI right on it.

maybe this will help you nvidia and ati do the same thing they have bunch of companies that make there cards and each company makes there card alittle different let take for a example lets say that visiontek xtasy 9600 pro and the gigcube 9600 pro they will be alittle different then each other some times one company make the cpu faster and the other company make the ram faster but what you want to do is look up infomation on both cards and see what is different and when you find what is different look up the 3dmarks score of each and they also put different software like games. when you look up the info you pick out the one that fits your needs. as for the defference in the gpu and the ram speeds the more gpu speed the more info it runs but as for ram speeds they help you use antileasing
i hope this helps

Yes, it will line up.

ATi licenses their technologies out for other companies to produce their products, most of the time at a lesser cost to the consumer. What you'll be getting is a reference 9600 Pro with a different company name on, but branded by ATi at the root level.

ATi didn't start doing this until two or three years ago. It's the best decision they ever made.

im gonna get a pci video card for now and in the summer im gonna build my own computer with a AMD 64-bit 3.8GHz I found.