It sounds like your looking at a fixed screen. A high end screen will set you back double (or more) of that $600. Look at Stewart Filmscreen, Inc. Their Firehawk and Studiotek 130 are two of the best and are well over $1000.
Carada make very good screens that are much closer to your budget (even if Projector Central didn't give them very high marks - they didn't test the Brilliant White version though). David Giles, the owner, is very helpfull and will bend over backwards to make sure his customers are happy - factory direct, internet orders only.
No, I don't work for them and I own a Da-Lite screen (needed a pull-down for my LR/HT room). I got my screen for well below MSRP, including shipping.
[Edited by Rasafras on Mar 29, 2005 at 2:07 AM]