The 3B active is small enough that it's decently fast even with experts offloaded to system memory. Any PC with a modern (>=8 GB) GPU and sufficient system memory (at least ~24 GB) will be able to run it okay; I'm pretty happy with just a 7800 XT and DDR4. If you want faster inference you could probably squeeze it into a 24 GB GPU (3090/4090 or 7900 XTX) but 32 GB would be a lot more comfortable (5090 or Radeon Pro).

122B is a more difficult proposition. (Also, keep in mind the 3.6 122B hasn't been released yet and might never be.) With 10B active parameters offloading will be slower - you'd probably want at least 4 channels of DDR5, or 3x 32GB GPUs, or a very expensive Nvidia Pro 6000 Blackwell.