You may benefit from Ryzen for that use-case. Ryzen has slightly less single core performance but has twice the cores of the 7700K. It also should be cheaper. More Cores means you can more easily Render with FL Studio or Video Editors in the background while still using other programs at full speed. Of course switching the build to Ryzen would mean a different motherboard as well.
960 Evo is a good choice, since that motherboard has M.2 slots. (if you were to switch to Ryzen AM4 motherboards seem to have at least one as well). Samsung tends to have some of the best SSDs so you can't go wrong with them.
Talk to 5 different people and you are likely to get 5 different recommendations for motherboard brands. For example I've always use Gigabyte motherboards where possible. A lot of people hold MSI in low regard because many years ago they were a low-end, cheap brand, like eMachines. However they've been relatively high-end for the last decade or so, and I'd expect they now have reliability at least on par with other reliable motherboard manufacturers.
You can get cheaper RAM, but it means either using 4 4GB sticks, which means upgrading Memory later is somewhat wasteful and more expensive (you have to buy a whole new kit rather than add another 2x8GB sticks), or it means using less reliable, cheaper brands which probably aren't worth it.
The Seagate Barracuda drive looks to be an older model, more importantly, it is a model that has known firmware problems which lead to it inevitably failing relatively quickly. I had a 1.5TB model and it died after 3 years. This is probably why the price dropped. Might be worth swappiing in a different drive, or even a different model.
Power supply is a good choice. You would be able to use a 650 Watt model without issues, I expect. And of course there are non-modular models that are cheaper but are less pleasant to work with in the case with their permanently attached Cthulhu of wires.
For the case That one looks like it should be relatively good to work with internally.
You can get cheaper cases but the problem is once you start going to cheap the case reflects that; sharp pointy sheet metal pieces which bend easily, screw holes that don't quite line up aren't uncommon.
