So, my thoughts are ...Sputnik already has decent spacial Fx built in (chorus and reverb/room ) so it should not be a major hardship to limit external FX to EQ, Delay ( unmodulated ), and dynamics (Compression/gate/limiter) plugs only in addition to Sputnik.
..if Ruby Tube is used as a 'warmer', then it probably passes as compression and EQ.
Stereo field expander .. no probs that I can see, and the exciter as far as I'm concerned is more or less an EQ if not used in a way to misrepresent sounds from Sputnik.
External reverb is out though .... on account that Sputnik already has reverb.
Hope that helps

