I have a trane XE80 furnace that uses 6 AMP or 700 watt power when the blower fan is running. Is that reasonable for this unit? An AC guy checked the system and told me that I have a motor or Run cap problem. He changed the Cap and it did not reduce the power. Then he wants to change the motor. Is it really problem? What should the power consumption be for that unit?

I am not an HVAC guy - just a technical guy, but power in an AC circuit is Volts x Amps x power factor ( ~0.7) - so 120 x 6 x .7 is about 500 Watts
If power is 700W for just the motor, it feels a bit high. However, if its 700W for the entire furnace - it feels OK. Since capacitors are used to correct power factor (reduce wattage), If the blower motor a Cap Start Cap Run, Cap Run, or Permanent Split Cap, then the guy might be right, but check see if you can get a 2nd opinion from Trane