Sophia Electric 300B Amp

Are any of you guys using one of these amps? Have any of you heard one of these? If so what did it sound like?
Just purchased a pair of 300B 91-01 mono's to run my Khorns. Looking for a good pre amp or dac/pre to match up??? any thoughts??? all music...
You may google "Sophia Electric 91-01 300B amplifier" for answers.

Here is a link for one:

I actually use Studer A727 to drive my 91-01 directly. A727 has variable output that can drive Sophia Electric 91-01 well enough. You may Check search DAC with volume control if you prefer computer output, or vintage Studer/Revox/Philips/marantz cd players with variable output for traditional CD discs.