If you are wanting to promote more muscle mass on the bike I suggest using bodybuilding's BIG 4...
Whey Protein
Creatine
Glutamine
Multi-Vit & Mineral.
Let me tell you, If your a cyclist and your not taking Creatine you are at a MASSIVE disadvantage, since its a latic acid buffer. BUT, I wouldn't take a creatine brand which promotes water retention neither. The added weight weight is very unessary and will just make you look very bloated. A creatine brand which I highly recommend is San V12. It doesn't promote water retention but just lean muscle mass.
If your wanting to gain more muscle mass I sugest taking Whey Protein along with your Creatine.
I definately believe guys like Armstrong, Millar etc have there own favourite brands of creatine which work for them. These guys in my opinion take creatine, no doubt about it.