Big Will,
David Hafler was an engineer who designed some classic components in the '60s and early '70s--the Dyna stereo power amps, tube and solid state. He left Dyna and started Hafler, which never really flourished. I'd be wary of SS gear that old. .
Historical note: Hafler kick-started the trend to surround sound by developing the "Hafler" surround scheme. If memory serves he incorporated it into some of the Dyna preamps. Everyone I knew tried out the Hafler circuit and the demo LP (vinyl) of choice was Joni Mitchell's Miles of Aisles. It decoded really well and pushed all the applause to the rear channel.
Regards,
