Hi James -
I'm not sure what you expect for duplicates - Aperture will not import duplicates (based on their file name I assume) if you tell it not to, but it doesn't have any way to do some kind of artificial intelligence duplicate search.
One solution is to use the list view in the browser, and try order by date, or by shooting date, or other - then, you may be able to identify duplicates adjacent to each other in the list.
For Boost, it really is up to you. I tend to leave it at default, except when I have a very contrasty image, or a serious highlight recovery issue. Then I wind it back quite a way. But I don't have an A900 (in my dreams...) and so I can't offer much specific help there. There's no rules really. Boost is just one of the tools you have to interpret the RAW data to your liking.
Hi David , the thing is ,a lot of pics that came from Iphoto are duplicated or triplicated sometimes , and there are quite a few , and I've never found the way to do it fast .
And Boost I now always use at 0% , have a go , then go for levels , etc etc you might find better results , as you have control over every thing , the other way you are working on a precontrast setting you might not need.
Let me know what you think , if you don't mind of course .