Thought you may like to see this; Ilkka did the test on HTS.
Yep saw it and integrated the info into the FAQ earlier today
I know Thomas recommends it to boost the signal for pro-amps but it looks pretty icky. It's almost -6db @ 20hz
There are a finite number of options for these kinds of devices. The Behringer DI-800 maybe a viable alternative. But the best option is have enough driver output not to need one of these in the first place.