turntable newbie: need advice for better sound

Recently bought on Amazon the Technics SL 1200MK and a Shure M97XE cartridge to go with it. Got an old guy in a record shop to set it up for me. Got it home and... I'm very ambivalent about the sound. While the soundstage is wide and there is definitely "air" between the different sounds, there is very little detail--sometimes I can't even tell what instrument I'm listening to. There is also a dullness (perhaps "darkness") to the sound and a lack of 3-Dimensionality despite the wideness of the soundstage. what else? Some distortion.

I learned enough to successfully change the tracking force from 1.25 (with the M97XE brush down) to 1.50 (with the brush down) and that actually got rid of a little distortion. Even that, however, makes me a little suspicious since 1.25 is supposed to be optimal.

ANYWAY, I'm looking for better sound. Any thoughts, advice?

The Technics is wired directly to a Mcintosh MA6500 and plays through Sonus Faber floor standing Concertos.