This is the tricky part (well sort of), Generally, Pentiums excel at image editing and Audio/Video encodeing (but you don't need to worry about the latter) and AMD Athlons excel at gaming. But recommending a new Athlon 64 3200+ or 3500+ is my suggestion. The new A64 socket 939's are plenty powerful enough to do what you want and will be much more future proof than Socket 754 is.
Now, i don't know much about Uero pricings but i'm guessing a Motherboard and CPU will get you pretty close to your 250 € threshold.