I'm glad you have sourced your problem. I discovered the same reason for lack of bass with Quad 63's some years ago. Couldn't stand them, took them off their stands, put them on the floor and they became a "full" range speaker! Mid/upper bass suckout from loss of floor reinforcement which the designer incorporated into the initial design.
Now that you have your attention on the speakers and their placement, if you have not already done so I would suggest that you do some reading up on proper placement of the speakers and listening position, how to avoid or take advantage of room nulls and nodes, taming first reflections, adjusting speaker toe in, ad infinitum. Buy yourself a Radio Shack SPL meter and a test disc and learn how to use it to your advantage.
This should keep you busy for a year or so and in the meantime you won't waste any money on new equipment. When you're done I suspect you will be amazed! :-)
Now that you have your attention on the speakers and their placement, if you have not already done so I would suggest that you do some reading up on proper placement of the speakers and listening position, how to avoid or take advantage of room nulls and nodes, taming first reflections, adjusting speaker toe in, ad infinitum. Buy yourself a Radio Shack SPL meter and a test disc and learn how to use it to your advantage.
This should keep you busy for a year or so and in the meantime you won't waste any money on new equipment. When you're done I suspect you will be amazed! :-)