Add a step-up or Upgrade

Hi I really need help here. I just bought a Shelter 501 MK3 installed on a VPI Classic 2 before I had a Sumiko Evo Blue Special My concern is the I have a Mark Levinson No. 25S Phono with separate PS but is the MM version therefore do not work well with the Shelter. I have 2 options Buy a step-up transformer like the Bob Devices Sky 20 or sell the Mark levinson and get a MC Phono Stage like the Manley Chinok I have no idea what will be the best way to go the ML 25s is amazing I also dont know how much to ask for it if I sell it. Please I need some input. Thanks.