upgrade advice from a Linn LP12

Jim, I think you have asked a question that depends on your definition of "improvement".
Your current TT is very good, IMO. I was faced with a similar question last year, and went the Linn upgrade route with a new bearing, sub chassis, power supply, base, etc.
I now have a MUCH better TT; that is IMHO competitive with other TT's that are multiples of what I spent. Therefore, I would suggest you look at the Linn upgrade path as your first option.

Bpoletti, when was the last time you listened to a current spec LP12??
Your comment tells me that it's been a while, LOL.

Jim, If you wish to switch from 33 to 45 rpm easily, any of the Lingo power supplies will allow you to do that. I replaced my Valhalla with a Radikal power supply and motor, which while more costly than a Lingo, was a MAJOR step up in SQ.

There are a number of more costly and complex tables on the market today, BUT I still believe a well set up and current spec LP12 will gave any of them a true run for their money....and leave most of them in the dust.