I have some questions too. I am a new I9305 owner.
I have the 4.3 bootloader, I don't care about Knox as I have no warranty (phone was 2nd hand). I've already tripped Knox anyway after flashing Philz recovery and rooting with it.
I have two requirements really, which I think are more kernel-dependent than ROM-dependent.
1) White balance/colour calibration. I hate the blue-green tint to the whites.
2) Wolfson/Boeffla sound controls for the Wolfson DAC.
I don't really care if it's Android 4.1/4.2/4.3/4.4, AOSP, CM or stock.
So far I still have the Samsung stock 4.3 ROM but I've flashed the AGNI v3.8.5 kernel which has given me some sound controls, but nothing useful regarding the display. Ideally, colour multipliers, black level, gamma etc.
The Perseus kernel+Stweaks looks like it might fit the bill, but I think it's 4.1.2 only and I'm not sure if it works with the 4.3 Knox bootloader? I'm happy to switch to a 4.1.2 ROM if I can, I just REALLY want to be able to fine-tune the screen!
Maybe there are other kernels that support this for 4.3 or 4.4? Or do any CM builds have the screen controls in the ROM itself?
I went with CM11 and AGNi CM kernel. It supports MDNIE hijack and although the AGNi kernel tweaks tool doesn't have any useful screen controls, I set the white point via an init.d script. The AGNi tool's MDNIE hijack setting must be left off, but the MDNIE hijack sharpness can be turned on and off as desired.
I think there is large batch variation with screens, as I see people reporting yellow tint, pink tint and green tint. My particular screen has a green tint, so I pulled the white_green down from 248 to 225, lifted the black from 0 to 10 (remove black crush) and lowered saturation from 24 to 15 which is probably still a bit oversaturated but not as cartoon-like as the defaults. The white_red and white_blue values are still the default values.
#!/system/bin/sh echo 1 > /sys/class/mdnie/mdnie/hijack echo 15 > /sys/class/mdnie/mdnie/cs_weight echo 10 > /sys/class/mdnie/mdnie/black echo 255 > /sys/class/mdnie/mdnie/white_red echo 225 > /sys/class/mdnie/mdnie/white_green echo 241 > /sys/class/mdnie/mdnie/white_blue