You mention memory stick duos... the only SLRs that use that are Sony, obviously. These are very good cameras, and they have some very good and/or unique features. But there are things that are less desirable about them. Cost of Sony lenses tends to be higher, especially as you move up to more premium lenses. Non-standard flash shoe, which means it's that much more expensive to enter into radio trigger flash land. And Sony has weird policies on pricing for their authorized retailers (I've heard from my local camera shop how they simply can't go below certain prices, regardless of how product is moving).
Oh yeah... personally, I think a maximum price point is a bit more useful than a minimum price point. 200 bucks, you can get a used camera body, and that's that.