Peavey has had a "post power amp" DI for many years. This one just has more options in it's ability to simulate various roll offs from popular speakers. The main thing about this unit, though, is that since it gets it's signal from the output of the power amp (presumably a tube amp), the resultant injected sound includes any influence made by the power amp section. On tube amps driven hard, that is a large part of it.
I have used the earlier unit EDI (equalized direct interface) for years with good results.