May as well, doubt the output will be that much, but then you wont get asked later on for that number. I'd also do 60 and 80 just to be safe on the top end too. Mainly so you've got a decent test of what most AVR's can crossover at for the LFE of a sub. I'd guess output should be about what the spec's is give or take, but again I'd just bench it once with a decent set of frequencies to satisfy as many folks as you can.
If its a pain to test at all those frequencies then I'd not worry about it, I just haven't seen near the bench test spec's for the XLS stuff I've seen for the iNukes like the 6000 which is what this is mainly compared to/competing with...
Also not sure how much its worth testing it at 8, 4 & 2 ohms for each. I'd maybe see what spec's are out there for the iNuke 6000 and try to get the specs of the 6000 at the same ohm/frequency so you can do as close to a direct compare as you can.
Personally I am not planning on running it at 2 ohms as I figure if I run 2 subs at 4 ohms, there will be sections it will dip below, and since its rated for 2, it means it should handle those dips without a issue, whereas a 2 ohm load dipping may trigger protection...
So not sure how worth it a 2 ohm load specs is v a 4 and 8... but I'm not nearly as smart as 99.9% of the guys here so I defer to you or others on that call.