Thanks for the prompt responses. I knew that more wattage would give me more power (and less range) but I was worried that the higher rpm motor might be sluggish during acceleration. The 500w/36v motor is not available in the lower rpm; that's why I was considering the 48v motor even though I was planning on using a 36v battery. I presume these are all geared motors although the listing doesn't specify. How noisy are the geared motors? What kind of range can I expect on level ground?