Hallo!
One thing I have notice is that 4429 needs more power to sing and the bass performance to be good. As other has said, including me, many times that room acoustics plays an important role. I don't have that problem in my room.
If you look at my measurements it goes down to 30-ish or so hertz and modal resonances is minimal in my room. Modal resonances will play funny tricks how the speakers will sound.
I do belive that a singel MC452 is a perfect mach for 4429. One MC275 is to little power.
If this is your final speaker placement as shown in post 113 then you have problems.
When I play music I have deep and tight bass performance with my 4429. My room is +70 square meters and +170 cubic meters of volume. Thank you very much!!Room acoustics treatment.