If you look at some of the outrunners the rc guys are using, they are more than powerful enough - some of the motors are rated at over 10kw continuous.
Most wheel motors for bike and bicycles are outrunners - the only real difference betweem them and the rc outrunners are details of mounting and outer shell construction - mere mechanical details. All these motors are PM synchronous motors, so they require one controller per motor. For controllers and motors visit rcgroups and related forums - they have plenty of detail on what is required.
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