I would first think about upgrading the phonostage. You would waist your money otherwise. If you want $1500 new cartridge you would want, say, $2500-$3000 new phono stage.
But frankly, if I were you I would replace the entire front end including phono and cables. You want a realy good sound and are prepared to pay for it. Then why not get it? Start with the phono and work your way up, or start with the table/arm and work your way down.