Yeah the 5850 all the way dude. DX11 and it knocks the 275 down all over the place. The 275 was made to contend with the 4890.
Just get on the auto-notify list for a few 5850's on newegg. just check your email often and keep the 5850 list on your screen and refresh it often. They come in, but go fast. That is how I got my 5870.... Which I just got today and was only able to install and download the latest drivers for over lunch.