Unless you can try it in your system, and so determine that it is an improvement, I would not buy a different phono stage at this point.
You like your ML phono preamp, so if I were you, I would buy a SUT from Bob's Devices. Per their website: "Returns are allowed within 2-3 weeks for full refund for any reason, less shipping costs, if returned in ÂnewÂ condition."
If the SUT does not work for you just return it. Then you can search for a suitable phono preamp if necessary.
Call or e-mail Bob's Devices and they will help you determine the best SUT to use for your cartridge and ML phono preamp.