Putting the accessories between the amp and pre- amp changes the signal emanating from the pre-amp. This is a strong signal but it might affect the impedance values seen by the amp and damp it somewhat. I don't know in this case but I think since it is all solid state it really would not be a serious issue.
Putting it in the tape loop places it in front on the amplification circuit in the pre-amp (i.e. between the source and the pre-amp).
Most would suggest it be placed in the loop because it might only be used occasionally and it would be easy to just switch it out. I have no problem with that, but I do think that the potential for having these devices before the amplification section of the pre-amp might create more degradation in sound quality than having them between the pre-amp and amp.
For example (my suggestion) putting the equalizer between the pre-amp and amp. I think many folks would value an equalizer for room sound correction and it's likely to be a set and forget event. Now if you value an equalizer for altering the tone of a source (either soft ware or hardware) then the tape loop makes perfect sense - you do want to change the tone before it hits the pre-amps amplification section anyway.
I would think that using the 'dynamic processor' would only be an occasional event and appropriately put in the tape loop but, again, if this were to be used constantly between the amp and preamp would probably be best.
Most equalizers also have provision for adding another processor in a loop (used to replace the loop it preempted on the pre-amp). It is possible to use this loop to piggy back the 'dynamic processor' and be able to turn it on or off at the equalizer.
And FWIW, a lot of folks might just no hear a meaningful difference in sound regardless of where these items are place, there are just too many variables, including our ancillary equipment and listening skills, to predict what anyone really should do.
