Have been thinking about going that route as I have installed the TKO500 in a c2, and know of few friends that are very happy
with their installation in their C1's. Depending on your rear end ratio (3.70 - 4.10) it can make highway driving much more comfortable with overdrive keeping engine RPM in a reasonable range. On the other end, a low numerical ratio (3.08 - 3.36 ) benefits from the deep 1st gear for off the line acceleration and less clutch wear.
Pretty much a win win if your T10 needs replacing.