RE: What do u think about the Mammoth?
Since I bought my Mammoth from my LHS, I was able to ask about hop-up parts and was shown thta they carry a complete line of replacement parts and also some of the XTM hop-up parts. This made me feel better knowing that I could come down to a local store and get the parts that I need if I break something.
Good advice is to check with your LHS and find out what they are going to carry.