What's wrong with my system?

That amp is 40 watts/ch I read. Also an integrated which usually means smaller power supply, less current capable, etc. compared to separates.

SPeakers are average efficiency at best, not high efficiency that enables use of fewer watts for good bass.

Based on that, while stating I have never heard the amp or speakers, I suspect you would hear a difference in the bass at moderate to higher volumes using say a good quality 120w/ch or more power amp. Is there any way your could try a more powerful stereo amp or even monoblocks as an experiment? I would expect a difference. If it worked and you Arcam has pre-amp outputs, you could use it as pre-amp only still perhaps with separate power amp at first and see how that goes from there.

That's not to say the other potential setup or configuration issues already mentioned should be ignored. Those would have an effect as well regardless of amp used, so I would recommend making sure what you have is set up properly first before making any change. Then you will be at a good place to consider equipment changes/upgrades.

One other thing worth mentioning is that good bass is inherently a problem at low listening volumes due to our human ears. Its a normal thing but something that bothers some. The common solution in the old days was a "loudness" button, which provided an artificial bass boost at lower volumes, for better or for worse.

You want to listen at higher, more realistic volumes to better assess bass performance. Bass requires power so listen at higher volumes to best determine where any real issues with bass levels or quality might occur.