Bass Traps

One ting that comes to mind is that, because of the reduced reflections, you are able to hear music better and that is why you might have raised the volume? Also, are the GIK 244 directly behind your seating position? Can you try to move them to the side and then check what happens? I do not have the "Sound Blocks", but play with their placement as well. From experience I can say that placement of the panels makes a huge difference. For example, if I try to place a 244 pane on the second reflection point in my room, then it simply kills the musicality and makes it sound lifeless.

Best thing to do would be to check with GIK themselves.

Because you were overcompensating due to lack of proper acoustical treatments.

Couple of things.  One, taming a very live room by controlling mid and treble reflections makes the bass stand out more prominently, so this could just be mid/treble absorption.  Another thing that happens is that valleys are reduced... if you had set the bass level based on the "average" bass level then that just came up a great deal.

Usually we find the opposite is true though, usually some exaggerated room mode has so much output we have to reduce the subwoofer level, and then find when we've clipped those peaks we can now bring the sub level up and it sounds much more full and complete.