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?

128x128gillatgh
I think that handling your power well and a new DAC are what you need. I'm not sure how the MC 12 does with analog.

Here is my current thinking and experience on AC management:


https://inatinear.blogspot.com/2019/04/power-management-for-frugal-audiophiles.html

Best,
E
gillatgh OP
At what point is an external D/A converter warranted or beneficial

Over a CDP, one good reason it becomes warranted is "if" the dac has clock output and the transport has clock input, so then the dacs clock can be slaved to the transport, so both run off the one clock through an extra bnc coax or even toslink lead.
As it’s always better to have one clock for both, that way transport and dac are in sync with each other, just like stand alone CDP’s are, as their transport section is running off the same single clock as the dac section.

Quite a number of transport, dac separates have this, usually reserved for flagship models.
Arcam had a toslink one they called sync lock out and in, with the front button called Pro, on their top dac the Black Box 500 the transport was the Delta 250
DCS have it, MSB have it, Esoteric have it ect ect.

Cheers George
@firstnot 
I remember doing the copy CD’s to VHS thing back in the day when I had one on my rack, (still own but in the storage room) a Sony SLV-595HF. It actually did a fine job but lost interest real quick when trying to find certain tracks. Did the index thing with counter where every song was but no thanks. 

My Sony still has the remote and has detachable PC. A true Audiophile piece here. I’d sell it but I still have that big box of “Movies”. Seriously, it’s not for sale.
@adg101 That's the Sony unit I have in storage. Supposedly top of line back in the day. I agree finding a track was cumbersome.  Not much of a problem for me as I don't jump around much. I would/will hate the rewind though.