The 7750 clocks exactly the same as the 7850, one is more of a ploy to get 10 dollars more from someone who doesn't understand you can just bump the multi up one and get 2.8ghz without a voltage bump. Neither processor tends to go above 3.4Ghz on air.
The x2 250 is listed under Athlon II, not Athlon.
You had said Athlon, so I didn't want him going out and buy a more expensive Athlon x2 6000 instead of getting a Kuma which is oddly named for an Athlon x2 but is an Athlon x2 none the less. (Actually it is a Phenom with 2 cores disabled, but newegg lists them under the Athlon x2).
And to correct myself, the price has dropped on the 6000, but it is still more expensive then the Kuma.
And yes, the Kuma is outdated, but it is the cheapest of the duos that I consider still worthy to buy.