when you say "monitor is 19" 1280-1060," do you mean that your monitor has a max resolution of 1280x1060? I hope not.
Also, how important is the warranty to you? Because both, Sapphire and PowerColor come with a fail warranty of 2 years. But Sapphire threw in a copy of Dirt 3, at least.
XFX has a double lifetime warranty, which makes them much easier to resell once you want to upgrade. My experience with XFX has been nothing short of stellar. I've owned their graphic cards and PSUs and I recommended their products to close friends and none have failed me, yet. I would go for XFX.
Yes, Sapphire and XFX are good, I also have 3 HIS cards and they're running fine until now...
Like solomonshv says above, XFX has double lifetime warranty and Sapphire will give you Dirt3 for free, it's up to you, but definitely don't go for PowerColor, you'll better with XFX or Sapphire.