I would like to formally protest the comment that you will recieve a noticable faster Photoshop experience "because of SSE".
For that type of application, I would also go with a P3 versus an Athlon. Those applicationss are optimized for SSE
This is simply not true.
The only routines in photoshop that are SSE optimized are image manipulation routines and filters. Unless you regularly work with 1200DPI images, even a complicated smart blur or some such filter will run in an immesurably small amount of time on a 1Ghz CPU, regardless of SSE support.
The biggest slowdown in PhotoShop (and this is not something that is regularily "benchmarked"

is the manipulation and detail work on high-res images. For example, zooming in on a 600DPI scan takes some real CPU power to do quickly but more importantly, it takes BANDWIDTH. Since large images can't fit in the cache of the CPU, the SEE enhancments are useless and AMD's much greater memory bandwidth is a HUGE benefit.
If you had the cash and wanted to do hi-res 2D image manipulation, I would recomment the Pentium 4, but right now the price is prohibitive and they are hard to find.
Athlons consistantly beat the PIII (price normalized) in Content Creation Winstone- which most nearly resembles the activities of a Web Designer.
Plus- the Athlon is a better gaming system

for lunchbreak
One suggestion- don't overclock a business PC.
I've corrupted one harddrive full of work from overclocking troubles and I'm not about to repeat that.
Eric
Edit: I'm assistant webmaster at BXBoards.com and I do web-work and performance testing about 20-40 hours a week so I know what i'm talking about (just figured I'd validate my above statements for you).
PS. In case you want to argue- I do concede that the PIII beats the Athlon at Content Creation on a CLOCK normalized basis but with the Athlon so much less expensive, on a PRICE normalized basis is how you should be buying.