Save some money in the way oversized PSU and get a better CPU. The R9 285 may be an alternative solution not a lot slower than the 290 but less power consuming.
Actually you can't get a quality PSU for much less than that and a better gaming cpu will cost at least 100 dollars more than the Pentium. A PSU is not a place to skimp even on budget builds. If you watch the youtube video I provided you see that the 75 dollar Pentium competes directly with a 245 dollar i5 even when it's overclocked.
You are however correct that the system would work using a 500W PSU as long as it's a high quality one. I'm actually planning to make a build myself using the 3258 using a 450W XFX Pro PSU, document the process and post it here as a guide. I'm a bit worried about the PSU size but since I have it vacant I'll try to use it. The reason I put the 850W PSU in was that Amazon didn't have quality brands smaller than that (at least I didn't find them easily).
The price difference between a 285 and 290 is not too big ($180 vs $239) but when you look at certain gaming benchmarks...
You pay 25% more to get 36% more performance. It's a good tradeoff. And coincidentally that 36% is exactly the difference between having playable frames in BF4 and not.
