Then you want a device with real octa core, where each core work contemporanely, right? if i'm not wrong, on xda someone post a mod to do it on s4 exynos edition, i read it a year ago, but maybe i remember wrong. however I agree with you, this is the revolution that i wait, not a stupid octa core big.little, but apps must update to use all this power. i wait that day...
After try aospa, nameless and mahdi, i think:
Aospa is the best ROM for y300, best, fluidity, battery life, minimal style. My favourite!
Mahdi and nameless are very similar, mahdi is smoother but nameless has got more features. I like both but nameless is a bit superior.
However aospa for me is the best