New floor around the corner.

hi. I wondered if you could give me your opinion on the drawing. as you can see the old floor is been removed, and the the gravel foundations been done. the walls are hanging from the ceiling, and iam planning to use isopor (the white 5cm thick insulation boards) with 5 cm of concrete on top of it. should i leave the isopor boards? 5 cm concrete? or more? And is that a good solution to have the floors seperated, like in the drawing? any suggestions? i am not planning floating-floors or any of that. i really would appreciate your help. sorry about my bad english. this is going to be a recording room (the main one) with a control-room (medium sized room) and a vocal booth (on the left).