At risk of jumping on top of the dog pile, I have owned a couple of SL-1200s (a MkIII and MkV) over the years, and they were OK. I will agree with Elizabeth; IMO it is a somewhat better than average cheap Japanese DD deck with a mediocre tonearm. While I have not owned a KAB modified version, I have used one and didn't find it to be all that much better.
Personally, for the ridiculous prices that are being asked for a clean, non-DJ'd SL-1200 I would hunt for a Luxman PD-121 or 131, a Systemdek IIx, a Rega P3 or a maybe even a Sansui SR-939. If I was feeling lucky I might look for a clean Oracle Alexandria. Just my opinion...