I tried going the KAB route with a Technics 1200 MK5. I finally took the pluge and got a VPI scout. There is no comparison between the two even with the upgrades...the Scout is just superior in every way. Trying to turn the Techincs into an audiophile table is like trying to upgrade a VW to a BMW M series. JMO
Your post never mentions whether you had the arm rewired or added the trough, or what cartridge(s) were used in each rig. The Technics is more vulnerable to mechanical noise and in-room vibration, so what it sits on is critical--more so than an isolated-by-design belt drive 'table. Unless the Technics is isolated properly it probably doesn't stand much chance, but when it is, it does.
I recommend upgrades to the SL12x0 in this order:
Brass cones platformed on isolated butcher block or Isonoe feet
Speakers. What are you using now? There are some killer $500 speakers out there now. I saw a review 3 yrs ago for some stand-mounted PSBs that were surprisingly linear.