Hmmm, since I'm not a hardcore gamer, I suspect that the 4850s will do me for quite some time - I'm just trying to get more mileage out of the 4850 that I already have by pairing it up with another. When I do need to replace them it will probably be for a single card. But it does make me wonder whether an extra $50 - 75 for an 850w is a good investment.
Not to muddy the waters, but how does the KINGWIN LZG-850 compare (currently available for $149 from Newegg):http://www.newegg.com/Product/Product.aspx?Item=N82E16817121076
It gets a very good review on JonnyGuru, but it's new and I don't know what Kingwin's reputation for reliability is supposed to be like.