The 1450XLD was indeed produced, but in very low numbers. Problem with them is that most of the units people have in their collections are actually prototypes. Many have a 1050 drive mechanism installed instead of the higher speed option promised with the 1450. Plus the speech handler wasn't quite finalized so that function does quite work as advertised.
Bob Brodie, Atari's User Group Head, was the only person I had ever spoken to that owned one. He took it with him on his last day at Atari. If you can find him he might be willing to sell. I have no idea if he still has it however.
You can see a 1450XLD at www.atari-history.com if you are interested in learning more.
