Well, according to the main title you asked for a 560, thought the 550 was a typ'o. Probably the 465 is faster at gaming, but it also can be a very unstable card, i've had some bad experience with that card. A 460 would be better if a 560 is out of your budget range.
The GTX 460 is a good card and selling at a discount now because the model is being discontinued. You might also consider the GTX 560 (without the Ti) which is a little bit slower than the GTX 560 Ti but lower in cost - I think it is a good value buy - although the GTX 460 is a value buy too.
Here is a review of the GTX 560 - the benchmarks include comparisons with the 460 and 560 Ti. Read the summary on the last page, too.
The 465 was a junk card from the start like the 5830. The 460 on paper and in real life performance is a great card and got one my self but they are not made very well. They got cheap when it came to cooling and most tend to degrade over a few months to a year before kicking the bucket. I suggest that you stick with a more reliable card for the long haul because most have issues with the power vrm overheating and some have issues with the vram not being cooled either. If you got deep pockets or a steady income then go ahead and get one but you will have to work at it early on to keep it from degrading over time.
Oke, thats completely different then. IMO 2 x 570, but with ( small ) risks like microstutter. 1 590 will generate less heat and noise and the 590 will be a wee bit faster maybe, but to pay an extra 235 for that, i wouldn't.