he's recommending the FX5200 series because they are DOGGIE DOO cards.
If NVidia, FX5900, minimum. You can overclock them to 5900Ultra speeds. But if you're gonna spend that much money, radeon9800Pro is better/faster at 90% of all games. Neither one will leave you unhappy, just that radeon is better performance at similar price.
For midrange cards - Radeon9600Pro or XT is the way to go. I'd go with the Pro, not enough difference to justify the extra 30-40 bucks at the moment. The similarly priced nVidia FX5600 series just gets beat all to hell by it.
Note that the differences become aparent more as you turn on/up the quality settings like anti-aliasing and anisotropic filtering.
At low quality settings, the radeon/nvidia series cards are somewhat on par, but as you up the resolutions and anti-aliasing for a better visual experience, the radeons really shine over similarly priced GF cards at this point in time.
As for processor, I just got a barton2500, and I overclocked it by changing the multiplier from default (11) to 12.5 and now have a barton2800 for the price of the 2500 (180 bucks vs 90 bucks) - using stock cooling, too. on the other hand, people who get the 2800s can frequently run it at 3200+ speeds. YMMV.
But the processor upgrade won't give you as big a boost as your vid card - especially if your just going from XP2000+ to barton2500/2800+. insted of dumping the money into the processor, use your old one, and move to the next higher vid card. Then in 3-6 months, when processors are even cheaper, you can pop a 2500 or 2800 or maybe even 3200 in there for a smaller investment.
BB