I would suggest buying the T-Maxx and just selling the 2.5 as new (some people are getting as much as $160.00 on E-bay). That is just shy of what it costs for the Serio which I'm told is the engine to get for the Maxx. I'm still waiting for mine from Tower. When I get I will post what I think about it and whether its all that people say it is. I sure hope it is.