Tube pre-amp upgrade from Mcintosh C2300

If I want to upgrade my Mac C2300 tube pre, should I just move up within Mac line to Mac C500T or try an audio research Ref 5 or a Shindo Monbrison? Has anyone compared those?

My source is Linn Akurate DS player, amps are Mac MC402 and MC275, speaker is Wilson audio Sophia 2 with transparent Ultra cables.