When your under OS X does your 17" ASD support lower resolutions than 800x600 (like 640x480)?
Mine refuses to go that low and this prevents some apps from running (Quake 3 for instance).
Not sure about getting higher res than 1600x1200 though. What is the highest res supported by the Radeon? There will probably be a way of choosing non-recomended resolutions like there is in 9 in the final version.
It just so happens that I went to CompUSA today and was playing around with a cube/17"ASD setup while there. Very nice, BTW. They didn't have it running OSX, but it was running OS9.1. The max res was the same that you're listing. The screen is actually a diamondtron NF as opposed to a Sony FD Trinitron (not that there is much difference, visually). 1600x1200 on a 17" diamondtron or trinitron is unusual to go at a higher refresh than 60hz, so I was somewhat suprised it was 62hz. At that res, it looked "nifty" but wasn't really usable.
I'm currently running my Cube/450 on a Mitsubishi Diamond Plus 200 22" .24agp DiamondtronNF and it's a sweet screen at 1600x1200 (or about any other res). although it goes up to 18xx by 1440 per the spec sheet (at 72hz) it isn't a listed option in the control panel for either OSX pb or OS9.04.
I'd say stick with 1280x1024. That ought to put plenty of strain on the eyes!