We bought nixies from the same vendor 
Mine are those
http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=400174245756&ssPageName=STRK:MEWNX:IT
I am going to try to drive them at 170v and see...
After reading about your experience I was thinking that multiplexing and optocouplers should be the safest way...