Yeah I think flat enough is the right phrase. Their bass is definitely lacking but with a well configured sub (I set the crossover at about 80Hz I think) you can compensate. My only feeling about producing with a sub is unless you’re in a very well acoustically treated room, it’s worth checking your mix on good headphones and a few sets of speakers to make sure your interesting sub bass parts are actually coming through nicely. They are good though to really work out what’s going on in the sub frequencies of your mix. Also makes it really obvious when those areas are getting muddy.