Hi Karl,
Spaeking as a former IT Consultant, the first thing one generally needs to know before being able to help a client is your projected budget. Otherwise it's hard to know if you want a Heidelberg press or a desktop inkjet. Let us know.
I am unable to understand why you need to print PostScript direct. Can you elaborate? The entire professional graphic arts and print industry uses PDF. Adobe InDesign that I use for books has a variety of varying quality PDF outputs, up to very high quality print. It's not usual to output PostScript any more (in fact, I cant even find it in the menus). Furthermore PDF is PostScript internally. not some different printer language like the old HP printers used etc.
Can you elaborate more so we can understand what it is exactly that you are doing?
As a quick comment. Epson make photo printers for high end photographic use that have specialised sets of black inks to give very great greyscale capabilities. You may want to look into these. Many artists still concentrate on black and white printing as a fine art, and are pretty fussy about blacks!
Andrew