At what point is an external D/A converter warranted or beneficial


Over the years and after multiple "upgrades" I've become disillusioned with digital audio reproduction. As my systems improved in quality/resolution, the digital audio quality has equally deteriorated to where most listening is now done in analog. This makes my CD collection of in excess of 1000 titles pretty much useless. My digital D/A conversion knowledge is pretty much limited to whatever is done by the internal D/A converter of the equipment. That being a Lexicon MC12B processor and Oppo BDP103. As my choices of ICs went from basics to high quality resolution improved with a marked decline in digital SQ. I'm at a point where any Redbook CD presents a harsh, edgy, shrilly, bright, name it what you want, upper frequency. Changing ICs back to basic cables attenuates this along with resolution of the music played. You might say I'm at a loss. Do I live with less resolution or the digital limitations. I do not have this issue playing analog media. Would an external D/A converter be beneficial or a waste of money? 
Systems are: B&W 803D2 and surrounds,  Lexicon MC12B, Oppo BDP 103, AQ Columbia ICs XLR & RCA,  AQ Digital ICs,  Tara Labs speaker cables,  Rogue Pharaoh, VPI Prime . Analog front end shares the L/R front speaker and input from the Oppo. 
Is there such a thing as an external D/A converter for a H/T setup as the Lexicon processor is the oldest piece in the chain with most likely the weakest D/A converter. But how would that connect to avoid the internal processing.
Any suggestions or recommendations?

gillatgh
@noble,
A very interesting suggestion. Also easily do-able as explained. Not really sure what it would do with sub integration but that's not the point here anyway.
I'll try this over the weekend as time permits.
Thank you for the suggestion. 
Hi gillatgh,

     Great.  If you have good results, I can explain how to configure the audio on the Oppo's on-screen audio setup menu.for 2 ch stereo playback if you play your music cds through the Oppo.  I can also explain how to integrate your sub for both music and ht playback, too.

Tim
gillatgh
The Oppo is a pretty decent contraption.  My brother has the 105 and I noticed that it produced better sound in two channel than in 5.1.  There is some great Chi-Fi (eg Gustard X-26) running the latest ESS 9038 chip that could do you well in two channel.  You could use the Oppo as transport and the dedicated DAC for your two channell.  Also Okto will be putting out an 8 Channel that that has the best specs.  
https://www.oktoresearch.com/dac8pro.htm
I will be getting one.

Find yourself a nos dac Tube , some dac sound so digital which is a big turn off for long listen periods that not what you want , what you want is a analog sounding from your digital front end   I got a mhdt labs pagoda with balance and tube buffer sound very analog and natural   Hope that help