Don't expect new low end nVIDIA cards in the next month. By the looks of things, you're gonna have to wait a lot longer before they release anything.
I would go with the 5770 or a 5750. They own anything nVIDIA has at that price range, and they still win on features. DX11, SM5, eyefinity, less heat, lower power consumption, etc.
The closest card to a 5770 in performance would be a GTX 260 core 216, and the 5770 still wins by a fair amount when you use the newest drivers.
I wouldn't say the 5770 beats the 260, especially not the core216. In some games it will perform equal or better, but most benches show that the 260 just has a bit more horsepower.
I would go with the 5770 though in this case. The 260 is a bit more money in some cases(depends which one you go with) and it doesn't support DX11. Also, the 5770 is more power efficient.
Links please. . .Rerun the tests with catalyst 10.3 and a different picture emerges. The 5770 performs on par with a GTX 280, and the 5750 is close to a 260.
Links please. . .
That isn't going to do. One persons experience with a specific driver set is noting more than anecdotal evidence at best. The first link could be a pic of any uploaded test. The second link is not a fair comparison as the system used with the 5870 is different than the GTX 280. I would suggest doing some better research and getting links to actual tests before making your claims.