Sorry to bump this again... Now my nixie's are in, I'm beginning my build. Since I have many 5V 'wall wart' supllies from old phones/USB hubs etc., I was thinking of just using one of those and bypassing the 5V drop-down circuitry on-board the classic v6. But then I noticed that the HT supply is fed from VIN, not VCC. So would 5V into that not give it enough 'umph' to reach 170V? Or is it OK to use a 5V supply directly?
A 12V wall wart with at least 500mA capacity will do the job nicely and is easily gotten. Just make sure it's regulated: measure the no-load output voltage and verify it's reasonably close to 12V. I only mention this because I have some older "12V" units in my box o' warts that wander up to 16 - 17 volts under light load which is no good. Pretty much any unit you buy nowadays will not have that deficiency.
Look into it later when the dust is clearing off the crater.