The i5's are much more than just a gaming chip. They're a solid cpu all the way around and works very well with photoshop and illustrator even when rendering effects on 30-40mb raw images (around 4100x4200). The single core brute force pretty much scales throughout everything. Unless the 8xxx is faster than a 6xxx, it really won't provide much improvement. If the cores are the same speeds, throwing more cores at the problem won't solve it. More powerful cores is a better fix. Sometimes overclocking 4xxx and 6xxx is easier than the 8xxx/9xxx amd's. Less heat, less power draw.
There's a very slight difference between the two with a small edge to the 8350 but I don't think it's enough to justify buying a new cpu for. Same as with i5 3570k and 4690k. Or even an older 2500k. There isn't enough improvement going to the 4690k (even if it were priced the same as an 8350) to justify the upgrade. If you're going to invest in new parts looking for a noticeable performance gain, I'd suggest looking at intel personally. The lowest cost option that makes the most sense would be using a decent aftermarket cooler and overclocking your current 6300.