The Shure pads fit perfectly. For the fun I also tried to put the HM5 pads I had on my Renkforce CD340 and they fit too (just don't be afraid to pull the pleather, and yes, if you do so the HM5 pads might not fit HM5s anymore).
For the sound I cannot say as:
1/ I am at work so the environment is too noisy and I can't put the volume as loud as I would like
2/ both Shure and HM5 have a foam layer in the center that I don't want to cut, and as I am ok with the Sony pads I don't plan to put the "driver covering" away.
At least you know that some options exist. I will probably test and evaluate the change in sound with these pads (Shure and HM5) without any mod and AB them with the stock pads as I have two MA900s just to see to what extend the high frequencies are affected, but for this you will have to be patient as I don't really have time these days. I have holidays in September and unfortunately I am not sure how much time I will have before.