It's your money. But if you want hard facts, then ask them what the damping factor will be with a 1/2 ohm load. Ask them how they will handle 90 degree phase shifts at that kind of load. Ask them if the amp will tend to be "brittle" sounding at that load. And as Hackmaster above states, ask them how hard the amp will be working, and how that will affect tube life? Just the ability to deliver power at that load is impressive, but power delivery is not any assurance of sound quality. I am a tube guy, and own all tube equipment. I love tubes. But, I believe that this is a SS application, if I've ever seen one. And just as Hackmaster says, choose even the SS amps very carefully, since that speaker will shut down most of the SS amps out there. If the amp won't drive a direct short circuit without shutting down, it won't handle your speaker. It will have to be a feedback design that swings the output impedance into negative territory to provide damping factor. I believe that when you press these manufacturers into answering these questions, they will back off their positions. A good way to do it, would be to ask them if they will repair the amp for free, if it ever blows up or chews up tubes, from this low load. And that still doesn't guarantee you good sound. Even the best amp in the world will not sound too great when it is stressed to the limit, in terms of load. And when you are using all the current it can deliver, just to drive a simple load, what will happen when dynamics occur?
This is sort of like buying a 500 hp engine, so you can drive at highway speeds in 1st gear. What do you think will happen to the engine when you run it at redline continuously? How much accelleration will you have, when you are already at redline? I think that this is a bad idea.
