Keep in mind that while you can use a 50 watt attenuator on a 50 watt amp, you cannot use it for full attenuation. Most guitar amp manufacturers specify the output power as clean power. When you run an amp full blast, the output actually becomes more efficient, but distortion isn't accounted for. So under distortion/OD, an amp is capable of putting out as much as 50% more power than its rated for.
If you plan to just knock down the dB level a little, it should be fine....but if you want to fully attenuate that Nomad, you should follow the rule of thumb for speakers and get one that is rated at least 1.5x the output of the amp.
Wouldn't want you to hurt it....that's a nice amp.
