Have you tried submitting a ticket to AmigaKit? Weren't they working pretty actively with you in your other thread? I'd like to hear some input from them - i.e., if they could at least tell you what model of monitor they tested the system with prior to shipping to you, might be helpful.
Also, just a shot in the dark, but are you using a dual-link DVI or single-link DVI cable? I've had a few systems (not Amiga's) in the past that were picky about this. Good luck!
