Well with the Radeon 7850 available from $220 on up, there is no way that the 560ti is worth $225. The 560ti needs to be about $190-200 to be a good deal right now.
That said, the 550ti is also not a good deal for the money, as the HD 7770 is available for a similar price.
Relevant info:HD 7850 for $220HD 7770 for $120
At 1920x1200, 7850 is about 9% faster than a 560ti, and the 7770 is about 21% faster than the 550ti. The 7850 is about 52% faster than the 7770 and 85% faster than the 550ti. So, the 7850 is definitely worth the extra $100 if you have the money in your budget and want to play new games at medium-high resolutions.