The RC51 is an old and dated design. Dont do it to yourself. Unless of course you want to buy a fat bike for the sound.
The 929 and 954 are pretty close in what they do, and how they feel. The 954 obviously has more displacement, but it also has a stiffer frame and (if I remember correct) alittle different suspension.
954 get's my vote out of the 3 choices.
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Do you really have to start a thread every time you go on a ride and see a guy with no helmet on?
Does it affect you that much that some random guy 1500 miles away went and paid his own money for a 1000?
Do we really have to fight over who uses the back brake or not?
Do you have to argue over stupid pointless shit on the Internet?