Get yourself one of those electric bread proofing boxes. Then it don't matter what the temp in the house is. That's what I use.

I wouldn't mess with the motor. The wattage is immaterial, it's how the unit uses that power to mix. Kitchen Aides commercial 5 quart mixer which sells for around $2600 is only around 350 watts but operates at full speed and power at all times and has a transmission with a manual clutch and it can mix almost anything.