Nice to see that the $1000 segment is becoming a better value. This segment has always been the sweet spot for me of great current performance without big diminishing returns. I think you'll probably have to increase your budgets soon by 1-2 hundred though, it looks like you're having to cut some huge corners to build something for $500. Though, if you did stick with AMD the motherboard would not have been such a minimalist one.
SATA 6gb and USB3 may seem overkill for a budget build, but most people on a budget will continually buy little component upgrades to keep up ok, such as a new SSD later (when prices are lower), higher speed external drives for backup, processor, video card, etc. That being said, buying a mobo to run the AMD chip would have meant you can't later upgrade the cpu without buying a new mobo, while getting an i3 gives you more flexibility. Without a doubt, buying AMD is a bad idea right now, but I think that means you need another $50+ to get a decent intel mobo (especially since they're historically ALWAYS more expensive) for more upgrade flexibility and mobo lifespan with USB3 and SATA 6gb.