well a controller keyboard can be used to controll soft synths by pressing and turning buttons on a controller instead of using a mouse and pc keyboard, also using a keyboard means you can play notes live by jamming along, it's not something you need to be honest, but its something to get further down the line.

as for monitors, i wouldnt get the fostex pm04 as they only go down to about 60hz, not sure of the exact figure, but i'd save and get the fostex pm05's instead