I don't trust that link, they stated "8800GTs will NEVER be able to do 3-way or 4-way SLi [...]", this isn't true, Nvidia is doing 3-way SLi for the 8800GTX and Ultra FOR NOW, and then is going to introduce it later. Teh cable used for 3-way is one single cable connecting up 3 cards anyhow, so it's possible.
Of course the Crossfire would beat one single 8800GT, if it didn't, ATi would REALLY be in trouble
The 3870 is very close to the 8800GT, but as I and everyone else with a level head, have said, the best thing with the 3870, is the price advantage, and the fact it's actually available for sale, not to mention CrossfireX support and a much lower power consumption over the 2900Pro/XT.