stationg, please refer to this
existing thread for the TV.
To answer your questions, they are part of the same HX900 series and are essentially the same TV. HX90
9 just indicates the addition of an RS232 port. HX90
0 was what Sony was referring to the model as earlier in the year, but now it seems US/Canada will get the HX909 upon release.
Note that the price you saw was also listed on another US e-tailer in the beginning of the year and then removed, I don't think that that price will end up being valid when it's finally released.