I find that over the ear headphones work reasonable well for me, and probably provide the best bass short of sitting down and firing up my stereo system with a sub-woofer. That said I requested that the streaming equalization be set up on my KS8 aids to give more bass than it defaults to. The sound is pretty good, but again not up to my stereo. The car/truck audio is pretty good too, with lots of bass.
The Signia/Rexton/KS8 aids seem to have considered that open fittings kill bass and included the tools in the Connexx software to adjust for the loss when streaming. Here is link to how they do it. It includes some screen shots of the equalization section.
How to Fit Bluetooth-integrated Hearing Aids to Maximize Patient Satisfaction