Haven't tried the software Congo5 points to; I use the free GerberLogix that directly supports zip'ed gerbers (even drag-n-drop). Haven't tried all gerbers from Kevin, but a fair amount, and it seems to work fine.
@UFN depends on the current setting and rails ....400V rails and 20mA will give you 16W for two 10m90 ...upping to 450V will give you 18W ...
Load the PSU with 5-10k power resistors
I have some cheapo EL34s for testing
Thanks to all for your very kind words about the build.
The chassis is a standard Modushop Dissipante 2U/400mm. Customization also done by Modushop: Drilling/re-anodize the front plate and printing.
@Pars: the re-anodizing seems to result in a more refined finish