While your choices seem like a great build, I don't see how an APU is that bad. What exactly is the difference between an APU and a CPU? And seeing that the graphics card comes with the APU, how exactly does it "get graphics power above that of the theoretical maximum an APU can provide?"
Now... why is my build much better than an APU. Well the APUs aren't bad. They provide basic performance. But the 460 I suggested in my link is simply a more powerful graphics card. You can play on higher settings in a larger number of games. So what is an APU? It's AMD's term for a processor (CPU) with a highly integrated graphics unit (integrated GPU). Like the processor you picked out in your original post. That's an APU. The main selling points of those processors are that you get (relatively) very good integrated graphics for a price not that much above Intel's offerings. But even the integrated graphics of an APU cannot match the power of the better discrete cards - like the 460 I linked. The only way to get equivalent graphics power with an APU would be to buy a discrete graphics card like the 460 or better - completely negating the whole reason you would even bother to consider an APU in ANY scenario - the integrated graphics. So... the graphics power of the 460 is above the theoretical maximium graphics power an APU can provide (while using its integrated graphics).
The flip side of the APUs is that the processor is relatively quite slow on a per-core basis. The i3 is not. Frankly, my build is a nice combination of sales, and you'd be a fool not to take advantage of it
Your brother is simply wrong when it comes to his recommendation. You could replace the i3 with a Phenom II x4 if you wanted the right sticker on the side of your box, but you'd have to pay more if you wanted decent performance (overclocking). As you can see by the price of that used deal.
Unless you live near a microcenter. They have some great combo deals for AMD processors & motherboards. But that's an exception, and I already mentioned that.