'outboard' high end dac's


Can anyone recommend an 'outboard' dac to be used in conjunction with an Oppo 105d (sabre 9018 chip), which might improve on the somewhat thin sound of the Oppo, improve on the (decreased relative to the Oppo) clarity noted when a Denon 1713ud (BB chip) was A/B'd with the Oppo, and decodes DSD and PCM formats?
Thanks
seventies
I really like my PS Audio DirectStream. It is fairly high priced at $6k new, but there are used ones available for almost half that. The bonus is the firmware has been updated several times and each time it improves the DAC for free!

Send it to Modwright Instruments and let Dan work his magic on it! I love the rich tonality, sublime clarity, and sheer musicality of my modified 105D.

Cheers,
Oran

Thanks to those responding to my query.
Regarding budget, I suspect it will take $2-4000 to improve on the Oppo 105d, if that is possible, and I wonder if a unit such as the Luxman DA-06, which can be purchased from Japan for under $3000,00, would with its BB 1792 chips allow the best of both worlds, assuming the Oppo
allows switching at will from internal to external DAC...I need more
information regarding this.  I believe that high resolution DSD files currently offer the best digital sound available, and I wonder if decoding DSD as opposed to PCM is potentially optimized by one-bit or multi-bit DAD chips.  So thanks again for the info and any further
suggestions.
Bryston BDA 3.  Decodes up to 356 DSD and sounds fantastic.  Let me know if you do not have a  loval dealer.