I honestly have no idea. The Podiums maybe help with vibrations, but I don't think it would help with bass? But I am not an expert.
If you think the bass sounds good from where you sit, I would just not worry about it. In the end, do you enjoy listening to your system? That's all that matters.
You may not need any (or you may need a lot?) of extra bass absorption. It really has to do with your room geometry, where the speakers are placed, and where you sit. The guy from Acoustic Insider always suggested figuring out where the best place to put your speakers and the best place to sit is the first step in "treating" your room and that is free.
If you are sitting in a null, you won't hear much bass and if you are sitting in a node, the bass may sound too loud or weird, so you'd move your seat up or back to see if that helps.
Your original questions was about if you need to do anything behind your listening position. The challenge with your CD wall is that it could be very reflective and late reflections from that back wall could cause some issues. If it sounds good to you right now, again I wouldn't worry. If you want to experiment, try something behind your listening area that is not super expensive (couch cushions? Thick blankets? I don't know....) and, if you feel it helps, then consider purchasing or making something more permanent.
I have a window behind my seat (about 5 feet behind me) and I have two 4" panels on stands that I just put in front of the windows. To me, it helped a LOT. It was probably one of two room treatment things that made me go "yeah, I can tell a difference". But that was when I had no other treatments up at all. You already have a room that is treated so your experience may be different.