Should I sell my DAC

Selling the OPPO is a sideways move at best! There is nothing, repeat nothing, wrong with the DAC in the OPPO! The proliferation of DACs is driven by business profit motive capitalizing on the insecurity and gullibility of neurotic hobbyists. 

If you must have a new toy to play with sell the OPPO and buy a BlueNode 2i streamer. You apparently have abandoned the use and ownership of physical media! Read the editorial in the March Stereophile! 

Better to listen to potential units and compare, and only sell your OPPO after finding a better replacement. Versus selling the OPPO only to not find anything you like and regretting that you can't get the OPPO back.

To answer your original question, there are DACs in your budget that some would definitely consider a better choice than the OPPO, but there are also people would would have the opposite opinion. Without knowing what you find lacking, I think any suggestions could accidentally send you down the wrong path.

@ghulamr,If possible, retain the OPPO and use it as a transport. It is a great player for playing HDCDs. Get a separate DAC, if you can. Consider used DAC that were $2k, which you can get much cheaper now.