Greetings -
Yes, you can use the power brick - PSU-DVC-POE13V=
With that in place, you can use the EX60 touch panel with the SX20. The various 8" touch panels are basically identical from a hardware perspective, with the obvious exception of cable lengths. The EX touch panel has a 1.5m cable, whereas the C Series touch has a 7.5m cable.
Also - and this is crucial - you cannot use the handset with any touch panel that is paired over Ethernet. In fact, as you probably know, the only endpoints that support the handset are EX60 and EX90, and only when the touch panel is directly connected (not using the power supply).
/enrico