Hi, Majic,
My turntable is a Technics SL1210 M5G (which has the improved tonearm wiring). I have it sitting on threaded brass cones instead of the stock feet, which sit on a 1.5" thick butcher block cutting board, which sits on a pair of silicon gel keyboard wrist rests. I have the KAB tonearm fluid damper, an Oracle Groove Isolator sorbothane mat, KAB rubber record grip, and the AT150MLX is mounted on an LPGear ZuPreme headshell.
As for your second question, that is simply an individual matter. Pretty much every technology-based pleasure device--whether bicycle, sport boat, sailboat, camera, or audio gear--offers increases in performance for the money spent. And in all cases one gets to where the cost curve steepens considerably to realize a small--but often very noticeable and significant--increment in performance.
Where this point of diminishing returns occurs depends on the individual's ability to hear the differences, the significance the user places on this difference (e.g,, is it simply noticeable or musically significant?), and how available the funds are to enjoy the upgrade.
I will say this, however: The AT150MLX is definitely on the high-yield portion of the price/performance curve. I started with a Shure M97xE at $99. A few months later I got a Denon DL-160 at $180, which was significantly better in all ways. A year later I got the AT150MLX, which is only $70 more than the DL-160.
Of those three cartridges, I consider the AT150MLX the stone cold bargain. Although it was only an incremental cost over the DL-160, it represented a paradigm shift in performance. When I upgraded to it, I felt like it suddenly catapulted me into the high end--the entry-point of high end maybe, but it feels far more high end than the Shure or Denon ever could.
Knowing what I know now, I wish I could have saved myself the $280 and lower performance of the Shure and Denon, and bought the AT150MLX to start with. I still have no urge to upgrade from it. I'm listening to Brahms' Symphony #1 by George Szell & the Cleveland Orchestra as I type this and it sounds simply beautiful. It retains its trackability and clarity even on these large scale orchestral works.
