Worry about hop-ups after you know what you want. 25mph or track racing? If you want 25mph, don't waste an MR01 on it. You will not need a 25mph Mini-Z until you race Mod class at the PN World Championships.
If you want to go track racing, which track are you close to? How many laps have you ever driven at your local track? Have you ever asked the people at the track about what to get? Since they race there, don't you think they'd probably know the best about their track? I don't want to be judgmental but you need to know what you want and take your own steps to find some answers.
http://www.google.com/search?hl=en&r...=mini-z+racing