Best SLR under $600?
Here's 2 more to research:
The Pentax K5--- the upgraded K5ii just came out, and people who want to upgrade are selling a very nice camera in your price range. tHERE's also the K30 but I don't know pricing.
Another Pentax, without a viewfinder, and the one I own, is the K01. Goes for about $370 with a starter lens, that's actually pretty good. You can get a 2d nice lens with the extra $250 you save from your $600. This has a APS-C size sensor, and access to gazillions of current and legacy lenses. It also has focus-peaking and I'm having fun with manual focus.
I agree with the poster above who noted that the lens choice is as valuable if not more, than the body choice. These 2 options give you great lens choice.
I started out longing for the Fuji X100/s but with an interchangeable lens, found the K01 and haven't regretted it one bit.