HD 5850 1GB vs HD 5850 2GB vs HD 5870 for Eyefinity

Hello all,
I have been looking around trying to find a really solid answer on this, but my searches have done little to satisfy. My query is this: I plan (by end of July), to have an Eyefinity set-up, with 3 LG 23" LCDs, running each at 1080p res.
I need to decide which graphics card to get. I am between the
5850 with 2 gb of ram,
5850 with 1 gb of ram,
and a 5870.
The price difference from the 5850 to the 5870 kind of scared me off of it, but if there was a reasonable improvement using eyefinity (IMO, there is not enough improvement to justify the leap using a single monitor set-up with 1080p only to justify the price premium), then I would get the 5870.
Also, if I did grab the 5850, would 2 gb make a big difference with mult monitors compared to the 1 gb? If not, then I would just get the 5850 1 gb, and CF later down the road.
anyone have experiences running eyefinity with different cards and care to share any opinions?
anyone know of any benchmarks that detail eyefinity performance?

Also: Heard a rumor that CF disables one GPU when running eyefinity. Rumor? truth?

Any help is greatly appreciated, as always.