I am an ex 401 owner who migrated onto Lenco TT's, I am also an early advocate of the SPH Bearing.
I have had works carried out on numerous Platter Spindle Bearings and was immediately aware of the values that the SPH Bearing could offer at a very reasonable outlay, the selection of materials and the options on Geometries offered were both a no brainer. I own a PTP Solid Nine, with upgraded bearing, so have a good idea of how an improved bearing impacts on the GL 75.
Like yourself there are now numerous customers experiencing substantial improvements, and will not revert to the earlier in use option.
Quite recently I was demo's a 401>SPH Bearing mounted on a compressed Bamboo Plinth>Gaia Footers, with a OL Arm and a Sumiko Pearwood. This source was also mounted on Panzerholz Sub Plinths and AT 616 Footers. I can not recall any time when I was experiencing a 401 in use that impressed as much as this set up.
Additionally, I have heard the SPH bearings in use on quite a few TT's and have even been instrumental in encouraging a design for one that has a composite spindle, which when demo'd, has been the one that has been quite indelible with the impression it has made on a GL 75, the noise floor was just so very different.
The one additional element added to the design to have a non- metal/metal contact in the outer of the bearing housing interface, as well as within, proved to be something quite special as a design change.
I've a leaning towards bearing assemblies and materials not usually met, and keep close to a few who surpass my knowledge on the subject.
I can't vouch for how much the new Phon' and Cart' have added to the new experience that has proven to be very satisfying, but do get the bearings influence on your positive outcome.
It makes me smile that the benefits of the changes selected to be made, are now encountered and deeply appreciated by yourself.