As far as the Switchblade noise and impedance issues, I will say this:
1. The unit is dead silent and has buffered IO
2. However, and importantly, it is an instrument level device, and not 100% line level. So users have complained that it cannot handle a high signal pre-amp and that it overloads. My answer is as follows: yes, I can overload an input with say a high signal output of a clean channel of a TriAxis, sure. But frankly, I can just as easily lower the output of the TriAxis and put more gain on the power amp. For lead and crunch tones from say a Mark V pre-amp via FX loop. the signal is actually quite compressed, and it is very hard to overload a Switchblade with such signal.
So practically, what it means is that for each preset that you build, you do have to pay a little bit of attention to your gain, but in my case, it’s only for high level clean presets. It is totally manageable and quite worth it, because you can then use their GUI to build amazing patches. I have my H9000R connected via DB25 analog 8 in/out, and in the Winblade GUI, I have 4 stereo little H9000 icons which I can combine the in and outs any way I want. This eliminates the need to ask Eventide to provide such functionality in Emote. And very powerful as you can program patch cross fades via MIDI.
Anyways, there are many pros and famous guitar players who use the SB. My advice is to get the 16 IO if the goal is to use with the H9000 as the latter already uses 8 of them.