There are several things here that are incorrect. First of all this card is NOT a stock 6800. It is a special card that uses DVI connectors that have two parallel DVI signals in each connector. Thus two 30" monitors per card. The stock card allows for one DVI signal per connector.
The specs that NVIDIA are quoting are the specs for a CRT, not an LCD. Specs of LCD's are very different from the analog output to a crt.
The second point is that Apple has stated that a Pc with a card that has the same functionality can drive this monitor. Steve is finally regarding Pc owners as his customers.
Try this link:
http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore?productLearnMore=M9593G/A
This is from Apple's PDF, it explains a little about the DVI spec:
The DVI standard specifies a single connector that handles two different digital signal bandwidths: single link and dual link. At 165MHz, the single-link bandwidth supports HDTV and UXGA (1600-by-1200-pixel resolution) display formats. The dual-link bandwidth (transmitted over a single cable) uses the same DVI connection, but it supports much higher resolutions, such as the 2560-by-1600-pixel resolution of the 30-inch Apple Cinema HD Display.
In other words, DVI SL supports 1920x1200 at 60Hz or 1600x1200 at 60Hz.
DVI DL has double the bandwidth and supports a combination of rez and refresh that would use that bandwidth. Hence 2560x1600 at 60Hz. The confusion arises from the fact that with an LCD the rez and refresh rate is limited by the DVI bandwidth. If the card can deliver more, it doesn't matter because the DVI limits the output. DVI SL was designed for HDTV 1080p. It's "G5 only" on the Mac, because those are the only machines that have an 8x AGP port.