What makes you believe that the input to a Xantech connecting block which normally is connected to the output of a Xantech IR receiver, or several such receivers, is compatable with the output of an RFX9x00.

The IR output of a RFX9x00 is a carrier modulated by a signal and is normally used to directly drive an IR LED (an IR emitter). The output of a Xantech receiver is not the same signal. The 791-44 connecting block expects as inputs the output of a Xantech IR receiver.

The QAD (quick and dirty) solution which I often use is to get the cheapest Xantech IR Jbox receiver and a standard IR emitter and tape the two together so the receiver sees the emitter making an Instant optical coupler / signal converter. I normally put the combo in a radio shack project box and add some stereo jacks to connect it up. I often use multiple emitters from different sources. But then they have to be spaced a little away from the receiver so they can all be seen. The receivers cone of reception is narrow when very close.