I'm looking at getting a high-end 21" iMac (16GB RAM, 512SSD). I plan on using it to edit HD movies in FCP X (maybe 4K iPhone footage). Also, probably work with Logic Pro X. However, I'm wondering if 4K will be worth it? The reason is I've read some posts/review that the integrated GPU isn't 100% adequate to drive the 4K display. I don't know if people are being picky- or if this is the general consensus. Other option is the mid-tier 21" iMac (non-4K) with 16GB RAM and a 256SSD. Any thoughts?