If you want someone to design your system for you, you should be prepared to pay for the work. If you want suggestion, please be as specific as possible. For example asking about current transducers is more likely to produce a meaningful result than requesting a general solution.
Do the transducers need to operate over the 5 kHz bandwidth of the amplifier or do they need to handle the class D switching frequency (pulse by pulse current measurements)?
Are there particular standards for the class of device you are testing which need to be met by the measurement system? Traceable to reference standards? What accuracy and precision?
Does the measurement system need to control the loads or operating modes of the amplifier?
As you can see many more questions must be answered before your request can be addressed.
Lynn
