First DIY, help

Soo Im building my first 3D printer with Geetech RUMBA and 4 Pololu drivers for 2A stepper motors.

For other parts Im using 24V E3D V6 direct hotend, Titan extruder with 1.5A motor, MK2B dual 12V 24V heated bed, some switches and thermometers.

I need to pick a 24V PSU unit but Im unsure how much watts/amps it should be.
I calculated the current that will be drawn like this:
4A motors(8A) + 2A hotend(25W) + 11A heated bed + 2A for the board, lcd, thermistors.. etc = 23A
So the power would then be:
23A * 24V = 552W

If I add some extra power just to be safe id take a 650W supply.

Are my calculations correct here? Do I need to get a 650W supply or did I do something wrong here?
Also should I power motors , hotend and heated bed all through the board or should the heated bed be powered separately.

A Mk2B bed heater run from 24V using the 24V terminals has a resistance of about 4 ohms, so it draws about 6A. A 25W 24V hot end heater takes just over 1A. The motors will take nothing like 8A because the constant current drivers step the voltage down and the current up. Allow 2A for them. The board + LCD will take well under 1A. Total 10A @ 24V. So a 24V 250W PSU is just about enough, however I recommend you use at least a 300W PSU to have some margin.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].