As a turntable guy, I could be happy with any of the three you’ve listed.
The weak link of the Technics is (as others have stated) their tonearms and record mats. These are areas of big gains, especially if using modern MC cartridges.
The AMG, while beautifully executed, will most likely require an HRS Platform or suitable isolation to perform its best. Solely mass damped & rigidly coupled.
The SME are truly finished products requiring no additional updates or tweaks. Most recently even the tonearm signal cables have been upgraded to Crystal Cable which is electrically wired correctly for all preamps including the recent trend of transimpedance. Their tonearms are sublime. The suspended models from the M15 up even have captive tungsten bearings installed in their footers should any type of boutique platform be utilized they can be revealed.
High performance turntables can be thought of as race cars in that they will only perform at their potential when properly set up. Most qualified installers (without a sell agenda) will be happy to set up any new SME due to a lack of potential surprises other than the sound of the finished product.