Cheap : Reliable : Power Pick 2. Supercharging is the worst way to go and the fastest way to kill a VW engine. The AMR charger is a common swap, but limited to cubic inches, so a 1600 is about the max for that unit. But, it adds stress to the lower end components and much added heat. Sector's Subaru swap is also very common for VW's, but a little more complicated for a Sterling since you really have to work the radiator placement correctly. Subaru and "cheap" are relative to one's abilities - if you can't sort the wiring harness, expect to pay a fair amount for one pre-sorted or having one sorted for you. Then there are the added expenses of the radiator, associated plumbing, shortened oil pans... list goes on and on. Dollar for dollar and simplicity, a well built 2110 or 2332 VW engine will outperform any stock Subaru engine. Horsepower ratings are nearly identical as are the torque ratings. You will, however, pay for the pleasure of having someone build one reliably for you.