It's honestly astonishing how much quieter it made it! However, I think it sounds great either way and it's really only by comparison that the original sounds loud. I'm sure you'll enjoy your Leopold 660m even more than silencing your HHKB in the long run! :3 Still trying to get my hands on a 660c with a pink metallic case ;_;
As for mods, I can't seem to make up my mind! I have lavender WASD keys that I had on for a bit, but they clashed with my mint Meowcap and I don't have any more Taros besides the one on my white HHKB (which I REFUSE to take off). I may put those back on with my lilac Fugu.. Too many options!
Kudos has a pretty nice setup on his already, black with red modifiers and a bloodlust Frankenfurt, but I think he's going to change it again.