No significant difference between a Laser + trailer behind the car and a (big) person in the back seat..... Or are you asking whether there are mechanical issues regarding the installation of the hitch on your Impreza? If so, speak to the technician who may do the work.
PS: If you search the Forum, you will find other threads on this topic.
I would be really surprised if the Impreza could not pull a laser. Certainly the owners manual will shed more light on the matter. You're looking at approximately 150lbs for laser, spars, & misc and another 100-120 lbs for the trailer. A manual transmission is an added plus when towing, as you can gear down on steeper grades if you feel the car is struggling just a bit under the load. Braking should not be a problem either. I have a Subaru Outback which works great for both towing and cartopping.