I haven't heard the term "duel link" before with DVI. But I would guess that since there is a DVI-I standard in which both analog and digital are supported over a single DVI cable, that this might be what they are talking about.
If so, I think that the 811 is DVI-D (digital only) so I think that the "duel link" DVI-I cable might be overkill (but should still work anyway).
The Digital formats are available in DVI-D Single-Link and
Dual-Link as well as DVI-I Single-Link and Dual-Link format
connectors. These cables send information using a digital information
format called TMDS (transition minimized differential signaling).
Single link cables use one TMDS 165Mhz transmitter, while dual
links use two. The dual link effectively doubles the power of
transmission and provides an increase of speed and signal quality;
i.e. a single link 60-Hz LCD can display a resolution of 1920 x 1080,
while a dual link can display a resolution of 2048 x 1536.
Be careful with dual link DVI cables, they are overkill for HDTV use.
I would recommend staying with single link cables as dual link cables have caused problems in the past. On AVS a while ago (year) lots of people were having problems which were attributed to dual link DVI cables.