In addition to all the great advice already given, check the source component as well to make sure you don't have a setting that may filter out the low end.
To my ears, sometimes "analytical"/clean sounding DACs can also come across as shy on bass. Not sure about your setup but if the other recommended options doesn't help, you may want to try some trial and error with a different source.
I have the HX300 amp with my dual H frames (so not exactly the same as you) but I definitely hear a difference with the bass depending on which DAC I use. For one of my DACs, I have the same experience as you and it doesn't matter how much I increase the settings, it doesn't feel like all the bass is there even though overall volume is higher. Perhaps it is just too "clean" for my liking. Same settings but different DAC (and volume confirmed with REW), and it is all good.
I have also recently had the opportunity to put a small buffer after the DAC, and that definitely helped improve the bass as well!
Hope you can get it dialed in to your liking