I've used probably every small lavalier mic there is,CSB,AT 853,AT933,AT943,DPA 4061,Countryman B3,Sonic Studios DSM,Sennheiser mke -2
There all very good,but if your really looking for a upgrade in my opinion as i have used them i would say get Nick to make you Nbobs for either AKG or Schoeps(i only mention those as i have used them so can't comment on gefell or neumann)
AKG and what i currently am running Schoeps IS a real upgrade over all the small lateral mic movements.
Thats just my opinion ,i know the Line Audio sound very good but i don't consider it a big leap from your AT853 sc which i also used to run.