Power = Voltage x Current
350W = 24V x Current
Current = 14.58A
Therefore if you operate your motors at 24V, they will consume about 15A. However, when the robot climbs an incline or carries more load, the current will be higher, so you need a safety factor of about 1.5, increasing the current to about 20A continuous. All of the controllers in the R/C Controlled DC Motor Controllers category can be connected to your R/C receiver - just choose one with enough current and can also support 24V (for example, 1x RB-Dim-23, 2x RB-Dev-04 etc.).