I can think of no reason why a raised feeder would be good for a boxer. They're perfectly capable of eating from the floor, just as nature designed and intended them to
Moreover, raised feeders have been shown by successive veterinary studies to increase the risk of bloat in large and deep chested breeds (yes, I know the hype around raised feeders is for preventing bloat - but they actually do the opposite and *increase* the risk). Boxers aren't the breed at highest risk of bloat (they're about 11th, if I recall correctly), but they are still at higher risk than most. And since bloat is frequently fatal, and eating from the floor is nothing but a minor inconvenience (if that), personally I would give the raised feeder a big pass. There is a sticky thread at the top of the health forum with more information on the bloat research, if you're interested.