Comp USA / tigerdirect has them for $125 with MIR every other week or so, but they have not been on line recently.
(They had three on the shelf at my local compusa yesterday, but they are $135 at the moment I think)
I think my old 5770 is on par with the 550ti.
The 550ti just didn't fill the gap between the 550 and the 560 well.