Motor Wattage Confusion

I purchased an enclosed mobility scooter that has a 60volt system and is similar to a golf cart but nothing about golf carts is applicable except for the four wheels. It's heavy like one but it really only seats me. After I moved the seat back 2 inches and added 1.5 inch spacers. The performance is abysmal in my opinion and I want to improve the acceleration and slightly increase the top speed. It currently has a 1500w motor and I was contemplating purchasing a higher wattage and high quality motor motor kit, but I can't find any clear information on the subject. Everything seems to be about making major changes to the whole system and I don't think I know enough about it to do that much of a change. Can anyone clarify what a higher wattage motor would do for me. The one that's in it now makes a horrible high pitch whining at top speed and I'm hoping that a better motor will work better and quieter.