If you use 255 quads for 8k map with 32x32 components, then the overall resolution will be 16,321m. That will effectively make it a 16k map, not 8k.
with 127 Quads, even when editing Landscape, the memory doesn’t go over 4GB. I have used a fully textured map with foliage painted and memory usage remain around 4-8 GB depending on what I was doing.
If you want to use 16k map, then you are better off with tiled map with world composition, I’m not sure even CE5 can handle a single 16k map.