I promised myself that I would not buy into power supply discussions, as the likes of Paul are well able to provide what people need with a range of excellent options.
However if those few folks who have the experience and electronic knowledge to persue this, then I will contribute my ideas.

In my opinion the better way to handle the tranny problem is to obtain one which has two 18V-20V secondary windings and rated at say 5A
A suitable unit can be obtained from Jaycar in Oz for $55.00 and are rated at 8.8A no less!!. No doubt they are of Asian extraction so they should be available from outlets in the UK and elsewhere.

Paul correctly states that inrush current situations, can cause core saturation problems with toroidal trannys, as they do not have an air gap; 'Inrush Current Suppressors' can be used which limmit the current at switch-on no matter at what point on the sine wave.
These have a variety of characteristics in terms of current and restore time.

Also these current suppressors will help to reduce the initial secondary current through the rectifier diodes with large smoothing cap values such as 20,000uF-40,000uF, as the winding see an initial short circuit before the caps charge up to the working voltage.

Using the two 18V windings (approx 23VDC with a FW rectifier) Then one supply can be used to feed the motor Drive/Regulator circuit at 21.0V
The second can be used to provide the 21V to the other control circuits and be further regulated down to provide the 9V if required.

Shunt any RF by using ceramic and tantulum caps. as suggested in the reference circuits provided for the LM317.

In fact for a few extra dollars the better option would be to use 25V AC windings, which will give a much 'stiffer' regulated supply, as the rectified DC will be bit less than rt2 X Vac or in this case about 35V DC The max input Vdc of the LM317 is rated at 40V.