thanks again, i did find your first link handy, but this second link again i can't see how it would drive 5120x1600.
from wikipedia (on dms-59):
DMS-59 supports two DVI Single Link digital channels or two VGA analog channels from a single connector. The compact size lets a half-height card support two high resolution displays
someone editing wikipedia obviously has a different idea than me about what 'high-res' means.
also from wikipedia (on dvi):
Example display modes (single link):
HDTV (1,920 × 1,080) @ 60 Hz with CVT-RB blanking (139 MHz)
Example display modes (dual link):
HDTV (1,920 × 1,080) @ 85 Hz with GTF blanking (2 × 126 MHz)
WQXGA (2,560 × 1,600) @ 60 Hz with GTF blanking (2 × 174 MHz) (30-inch / 762 mm Apple, Dell, Gateway, HP, NEC, Quinux, and Samsung LCDs)
so i'm pretty sure it needs to have 2 dual-link outputs.