I'm not aware of any DAC's in this price range other than products like the Squeezebox which are a different type of component. There may be some however.

For $500 I would look at used DAC's if you already have a transport.

If you are thinking new transport/DAC, I would put the money toward a good one box player such as the Rega Apollo.

Two of the best "Value" DACs....

Citipulse DAC

Liteaudio DAC-60

RG