The arm you have is a pretty nice arm, and the usual choice on a Thorens table. I would look at different carts. It may just be the sound of the Grado that you dont care for possibly?
I personally havent listened to a Grado, less the Sonata, which didnt sound bad at all. My personal preference to carts is with the Audio Technica brand.
I have one of there MC carts and love it. Also have on a lesser table the 440 mla. Matches the table I have it on quite well to my ears.