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You're overestimating how fast the 7850K's GPU actually is. Specification-wise it's about the same as an R7 240, and since it doesn't have its own dedicated VRAM but uses system RAM instead it's going to be even slower, especially with the 1333MHz RAM in your build (which btw doesn't have nearly enough of it, especially for an APU). Even if he uses the fastest possible RAM (2133MHz IIRC) and crossfires it with an R7 250, the fastest card you can crossfire the 7850K with, it's still going to be slower than a 260X. As for the CPU part, the G3258 wins that, too; it matches or slightly trails the 7850K in multi-threaded performance, and completely trounces it in single-threaded. It also overclocks like mad; I've read about one guy reaching 4.5 GHz on the exact same board that my build uses without exceeding the maximum safe voltage, and at those speeds it completely obliterates the 7850K. The Pentium also has the advantage of being upgradable to something like an i5 in the future, unlike the A10 which is most likely the fastest chip that'll be released on FM2+.
Also, there's nothing wrong with the VisionTek card. You may not have heard of them, but they've actually been in the graphics card business since the late 80's, and they've been an ATi/AMD vendor for about as long. Admittedly I could only find one review of their 260X, but it's from a reputable site, and they seemed pretty pleased by it:
http://www.tweaktown.com/reviews/5917/visiontek-radeon-r7-260x-2gb-overclocked-video-card-review/index.htmlI agree that trusting his dad in supplying a case is a bit risky, but I wouldn't worry too much about it. My build uses a Micro-ATX motherboard, and both the 250 and 260X's I chose are pretty short, so as long as it has standard ATX mounting holes everything should fit just fine.
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