To run two pair of monitors from one SET amp

I have a Assemblage 300B Platinum amp which is running a pair of full range driver speakers. Nevertheless, I have fallen for a pair of AKG K1000 headphones, which happen to be really affordable and yet extremely inefficient. These headphones need their own amp, with a minimum of 7 watts per channel (Efficiency around 74db.) So, instead of buying a separate amp, I thought about getting a speaker switcher such as those that NILES makes. When I read the website information, it said that it would work with amps that can drive at 4 ohms. I think this switcher halves the impedance of the amp in other to drive two sets of speakers. These are the questions I have....#1-Will the NILES affect the quality of sound that goes into the monitors (both Speaker and headphones)? #2-Is an SET amp such as Assemblage 300B with three heavy transformers break a sweat working driving 4 ohms? #3 Which is better, get its own amp to drive the AKGs...because my preamp has two outputs? #4-If I go the way of 3, then, if I do not turn on the SET amp, it will not in any way affect anything down the chain, right?
Paul, i doubt if the switchbox halves the impedance. If anything, the switchbox may have impedance compensation built into it. This is a form of "protection" that simply RAISES the impedance that the amp sees if you have several speakers selected at once.

As such, they probably make the "4 ohm capable" comment simply to remind you that selecting multiple speakers can provide a low impedance load to your amp.

As to hooking up a speaker switchbox to your amp, that would STRICTLY be a matter of convenience. If it did anything to the performance of the system, i would say that it would be to degrade the sonics via the cheap wiring, switches and jacks that it would make use of.

Given the desire of some folks to do something like this, i have to wonder why nobody makes a high quality switchbox for situations like this ? If there is one out there, can someone point Paul in the right direction ? Sean
Making a switcher would be very easy and cheap.