Wow this thread has problems... dual 5770s will match a 5870 and beat out a 5850 by a good 10%. The scaling and compatibility issues were about two years ago, now they are not worth mentioning with only two cards. If you fully plan on buying a second 5850 in about a year or less, then get the 5850. If not then something better will be out then another 5850 for the money. 5770s are noticeably faster to be honest, I'm not sure what these people are talking about.http://www.legitreviews.com/article/1105/1/http://www.guru3d.com/article/radeon-hd-5770-review-test/
Read for yourself before you listen to the masses.