The XY motors need around 1A, so you have 4A remaining. The 555 motor needs ~2A for full speed without load, but could exceed 8A at full load (although it would get hot fast and eventually burn out).
I believe the Eleks board (PCB traces) and MOSFET would fail at full load before the motor, if your power supply could even provide enough current without shutting down.
If you care about speed control, you'll need a dedicated motor controller with TTL input. If not you could use a relay. T2Laser supports spindle delay to allow for it to start up before any load is applied, this really helps due to momentum.
@Atthis It depends on the wood but in general i use 100 'speed' for cutting. I have tried a few different types of ply at 2.4mm of which some cut in 2 and some in 5 passes. Really depends on the quality of the wood.