Yep, sure is. Horizons has been closed for a few years now. Sometimes I wish there was a way for them to move all the old rides to a part of the park called 'Lost Disney' like Kennywood did in Pittsburgh. That'd be pretty tough to do though.
Same location, but the Horizons building was gutted and redesigned. The Mission Space ride system is in no way similar to Horizons, except that the "cars" accomodate 4 people.
Good choices! I'd put Energy last on that list, though. TT and M:S are both more popular, and Energy holds a LOT more people per "trip." Get the two busier ones out of the way and then you have a nice leisurely ride on Energy to look forward to.