2GB cards don't really offer much of a benefit at the moment and it will take a while before games come out that can take advantage of more than 1GB. GTX 280s in Tri SLI will generally do better than two GTX 285s. As for the 4890 in triple CF I don't recall seeing any benches on it but I'm sure they are out there. Google is your friend on that one. The GTX275 is also a good option as it's generally just as good as the 280/285 in all cases except where the extra memory of the 280/285 is needed. Running the GTX275 in dual or triple SLI is something you should consider.
Actually, if I remember correctly, I think the most recent ATi cards scale better than the nVIDIA cards. Regardless, three 4890's are quite a bit cheaper than the other options and will probably offer a better price/performance ratio. Crossfire is also more universal than SLi.
If you were considering only the nVIDIA cards, the GTX285's would probably edge out enough to justify the price.
I am curious what the best amd motherboard is for tri-crossfire or quad-crossfire? I have 3 4890's and I am looking to upgrade to the 955 from the 940 and take advantage of the ddr3 available. I was curious if there is an amd am3 board that can run x16 x16 x16 or x16 x16 x8. I am a big dfi fan but my current 790fx M2rsh board only runs x16 x16 x4 and also since my cosmos s case's power supply is located at the bottom of the box there is no way to fit my extra 4890 so I guess I have to take that into consideration as well. I had purchased two 4890's at first cause most said it would be better than a 4870x2 but I am not seeing that on the benches I have ran. Also I think having the option to go with 2 4870x2's would have been a better option than 3 4890's or 4 4890's. Idk maybe I am just a noob to all of this. I was trying to set up an ultimate gaming rig and have fallen quite short. My 3dmark06 is around the high 17's and was hoping for at least low 20's :-(
Any help would be greatly apreciated.
thanks in advanced