You aren't overclocking or even video editing, so with an $800 budget there isn't any reason to go for AMD.
A few points:
-Personally, I'd leave the SSD as the upgrade and keep the r9 280.
-Since no overclocking and the build is now intel, you could really change the PSU to a EVGA 500w B1 as 620w is beyond overkill. It can be argued that PSUs can be used in rebuilds, but though I'd mention.
-Totally agree about the case. That thermaltake chaser was $90, 10%+ of your budget and the MX300 will do the same job for less. There are plenty of good alternatives under $50 if you don't like the look of that case. On the other hand, a case is reusable in future builds so a good one now might be alright. Totally up to you.
I would strongly suggest the Intel build over AMD. Tom Tancredi touched on some of the points; the FX is really dated compared to the newer intel chips. You will get far better performance from the i5, not to mention less heat/power.