His had the Vishay, so the one your eyeing should sound even better.
And they really do appear quite reasonable for what you get.
Cool logo, too!
I have a couple DIY preamps using fully balanced Khozmo stepped attenuators which I really like. Hattor is the brand used for complete preamps from the same company. I prefer an active output stage, which Hattor also offers.
I have not tried the AMRG resistors, but have read good things about them. My first build uses the Takman REX resistors in the shunt positions with a Vishay Z-foil series resistor. This combination sounds excellent with exceptional transparency. My other Khozmo use Takman REY shunt resistors and an Audio Note silver tantalum series resistor. I'm still working on tweaking this preamp which uses different power supplies and output buffers, so I'm not ready to say whether I like this combination better or not.
I have a balanced version with the AMRG Trans resistors. I am using it with an ARC Ref 75SE at the moment. It is superbly well built and the remote works really well. It controls volume, input, balance and has a mute. Once set up I am not sure you need much else. The sound is superbly natural, not surprising given there are only 2 high-quality resistors in the path. The only thing to watch out for is impedance mis-matches and it sounds like you have that sussed. It has equalled some very expensive preamplifiers in naturalness and clarity. If you want to alter the sound then this is not for you but if you want a neutral preamp then the value is great. It comes in a flight case and is really well made. I ordered a buffer input and all it required was to add a board, job done.