Sorry again. I thought I had responded to this!
Don't use the Crop Tool!!
This is a house image...
[ATTACH=full]150194[/ATTACH]
This is the Crop Tool being used on the house image....
[ATTACH=full]150195[/ATTACH]
This is the house image cropped......
[ATTACH=full]150196[/ATTACH]
This is the original house image resized using IMAGE > IMAGE SIZE.......
[ATTACH=full]150197[/ATTACH]
It is first resized to the desired height of 600px (or you could resize to the desired width...........depending on how much room you have).
[ATTACH=full]150199[/ATTACH]
With the Crop Tool, then crop the width to 900px by dragging the either the left or right side transform handle.
[ATTACH=full]150200[/ATTACH]
[ATTACH=full]150201[/ATTACH]
No loss of sharpness or pixelation.