Audio research use TE Connectivity AMP Connectors CPC Series 1 connectors.
Rated @ 600VDC.
Molex makes a line of circular connectors which can do the job with ease. Since you don't need much in the way of current and the voltage is nominal, you have a wide range of connectors you could use.
Its a good idea to bypass the connections inside the amp, so as to obviate the umbilical cable's length.