Recommend me a SE attenuator to sit between Khadas tone board and Hypex NC122MP please?

Khadas Tone Board output impedance = 100ohm
NC122MP input impedance = 47Kohm

If I'm not mistaken, something around 10k impedance should be appropriate.

The cheapest, simplest (decent) option I came up with is an ALPS RK27. But I know there are other possibilities.
There are some relay attenuators out there that promise to be quite transparent (and I've always been a fan of the sound of relays clicking)
Or step resistors. Khozmo if I decide I've got too much money.
Or should I go with a chip-based solution? PGA2310 or Muses maybe? I've been trying to settle on something for the last couple of days while I'm laid up sick on the couch, and I'm pretty sure I'm overthinking it at this point.

What would you go with?
Thanks for any input.

Here's a layout of my build to give an idea of the space I've got to work with.
KktON0g.jpg

As an aside, I've ordered this chassis for my build. Does anyone have an opinion on whether the radiator fins would be sufficient for the Hypex or do I want to be drilling ventilation holes?