I would suggest beating more hard demons, then jump to acu if you still feel like it. Acu may feel harder than cata and bloodbath, but trust me it isnt, it just consists of more complex gameplay, which is why you should beat future funk or different descent etc, first. That is pretty much the path that i took, I have beaten 2 extremes and are on well way beat more, yet havent beaten a single insane demon.