If you are not too bothered about the very latest eye candy and DX11, the HD4850 is faster than the HD5670 and can be found for under $100 US, but supplies are drying up quickly.
Also bear in mind the HD4850 draws more power and needs one 6 pin PCI-E connector to work, which the HD5670 does not.
Great 1680x1050 performance in most games, 1920x1200 in most games with lowered detail
The GeForce 9600 GT is still a great entry-level performer, thanks in part to its high-end 256-bit memory interface and speedy DDR3 memory. It's a solid choice on an $80 budget, even if the architecture on which it centers is showing its age.
While the GeForce GT 240 is beginning to encroach on this card's price territory, the 9600 GT remains a bit faster than even the GDDR5 version of the newer card, and its recommendation remains secure for the time being. It remains to be seen whether the new Radeon HD 5670 will drop in price to give the 9600 GT some real competition.