I love them.. It gives alot of power, for me it was what I needed to start maxing games with 60FPS!
I had some driver problems, and in some games that doesn't support xFire I wish I had a better single card, but other than that it's great! Really packs a punch and it is probably great for higher resolutions than 1080p or eyefinity as well..
I got the 5850 for very cheap, and for that it is totally worth it! I guess you can find a cheap one at your location as well.. Great bang for buck.
They do need good cooling though, which a HAF X has, can you have 1 pci slot between them?