Antique Sound Lab ASL HB1 Headphone Amp?

Has anyone taken a look at this headphone amp?

Its looks pretty simple and reasonably priced compared to other headphone amps. And if Class A and tubed, wondering if it might sound pretty good with high resolution headphones?

I now have several pairs of headphones, a Grado, HeadRoom and NuForce headphone amp, but don't really love any of them.

Wondering if the Sony MDR 5000's on sale for $350 might be worth a try.

I like my Audio Technicas for casual listening, but I would like to updgrade while spending < $1000.

Thanks for any ideas.

Would this make replies easier?

For $300, it looks more substantial than a lot of other headphone amps I have seen, but no dealer in my area as far as I know....