IMO,
if you are looking for a light boxer engine, you are better off with the flat-4 turbo from Subaru (a lot of cheap engines are circulating around the recylers, plus some JDM stuff).
The problem with the SVX drivetrain, as some have mentioned, is it is fairly exotic, not too easy to find parts (for cheap nonetheless), and they do not like modifications at all (i.e. turbo'ing this engine is a bad move). Certainly need to consider this engine is not cammed for an off-road application.
Maybe going with the newer flat-6 found in the Legacy Outback might be better suited to your needs, but overall, do you want function or a novelty?