Andy Kim, Soundsmith, VAS, Anamighty Sound, etc. all can do excellent work on a 103...all for less than $1k. Imho if you spend more, as suggested above, other carts are more sophisticated. One noteworthy exception in the Sculpture A cart line manufactured by the wonderful Anamighty Sound in Paris. They take the magnets and a few other bits from a 103R and create a serious next level cart out of it.
What loading options and gain do you have in your diy phono?
What loading options and gain do you have in your diy phono?