The 2.5RS is a good choice but even a 2.2L has plenty enough power to take on large amounts of snow. When we were living in Upstate NY the 2.2L w/ studded snow tires would claw up driveways that were ice-covered and pull away from slush-filled intersections w/ the greatest of ease.
The price difference between 2.2 and 2.5 can sometimes be pretty big. Believe it or not eBay is a good place to find Subarus at a good price. A friend of mine just bought a 1999 2.2L Impreza Wagon for 7400.00.
As far as working on them, Subaru motors are quite easy to work on (I've worked on quite a few different vehicles). The amount of space around the motor and low placement in the engine bay makes it easy. This has to be the easiest car to change the oil on ever. You can catch the drain and filter oil easily in the same pan b/c they are so close together.
The 5-spd is great...I've never had any real issues w/ it. The clutch will shudder when cold but it goes away pretty quick and is normal.
The AWD system is a kind of passive traction-control "shifting power from the wheels that slip to the wheels that grip" (Subaru ad slogan
And lastly 'mt'= Manual Transmission
Hope that covers it all.