Are all of these devices compatible with our Hewlett Packard 4194A Impedance / Gain-Phase Analyzer? 

Yes.  The Agilent (HP) analyzer will work well with our injectors and so will all typical AWGs, function generators, RSAs and oscilloscopes.  You will not have access to some of the advanced measurement features using the Agilent analyzer, specifically the non-invasive phase margin; though if you can measure the output impedance you can convert that to Group Delay and then to a phase margin. The Bode 100 does this automatically.  Without the ability to measure group delay the conversion of output impedance to phase margin must be done by hand (Excel). The Bode 100 generally has better sensitivity and a lower noise floor than most other analyzers.