R2R and then the tape booster I believe. In this world of Nebula you have the ability to go beyond the real world applications and order things at will but I am sure that Michael has clearly suggested that it is the 'second stage' in his material- that at least is how I have read it although there is ambiguity. Hope it helps and do read Michael's very thorough documentation to be absolutely certain.
In words of Enrique Silveti, the correct way to use R2R + TB+ is setting the "in" parameter of the R2R Nebula instance to +6db, and the "out" parameter of TB+ between -6/ -8db, but I prefer set it in a point near to -6db here, but it´s my opinion.
After of this is necessary a no-Nebula compressor set to threshold -50 db, ratio 1:1,10 and fast attack/ release... or a VTM-M2 instance.