There are motherboards out there that support 400/533/800MHz FSB. Newegg just doesn't list them this way, but if you click on the manufacturers link it will give you more info. So you can do what you are wanting to do.
But socket 478 is old technology. Not much in the way of an upgrade path. Also if you are wanting to use the latest graphics programs like CS2, going to socket 775 is going to give you much better upgrade options and much better performance for high end graphics.
My suggestion is for the newer technology. And no it doesn't have to the best or most expensive out there. I understand what you are wanting to do, but I think there are better alternatives. It just doesn't make sense to base a core system upgrade on the ability to use an old CPU till you can get a new one.
If you still want to go with 478 that's fine, but you still need to give us a budget for us to properly advise you either way you go. Also current system specs/model so we know if your PSU can handle what we recommend, and what other components you will be reusing.
Also just so you know, if you plan on keeping you AGP card, going from 4X to 8X AGP slot most likely will not make a difference that you will notice.
8 Pro 64bit
AMD FX 8350
Asus Sabertooth 990FX R2.0
16GB G.Skill Sniper 1866MHz
OCZ Vertex 4 128GB SSD
HDD's 3TB/2x 750GB/500GB/250GB
2x XFX 6870 1GB
PC P&C 750W PSU
Cooler Master HAF 932 Red LED
CM Hyper 212 EVO w/2x SickleFlow 120mm Red LED
Logitech X540 5.1 Surround
2X Acer 23" LED - Eyefinity: 3840x1080
"The significant problems we face cannot be solved at the same level of thinking we were at when we created them."
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