Weak link

+1 @jsalerno277 It amazes me how much better my gear sounded after investing in noise management.  The more I invest the more the gear keeps getting better!

I have a CAD GC1 and GC3 and 3 Akiko Corelli's in addition to dedicated lines and a Shunyata Denali.  I also have a PS Audio P10 that runs the digital stuff.  And I have taken all SMPS's off my dedicated lines.  I had SMPS's on the P10 and it absolutely shredded the sound quality from my DAC and Music Server.

After that upgrade you cables.  If you can't remember the names of your Wireworld cables it didn't hurt enough when you bought them.  I think really good cable prices are ridiculous but at the same time performance follows price.  The difference between $500, $1000 and $1500 cables is evident and discernable with noise management.

I believe a lot of the benefits of upgrading gear is missed without addressing the above.

+1 @rikkipuu I never explored the grounding devices that are on the market but it is all a logical progression from good cables and power conditioning, to dedicated lines, to improvements in grounding to realize a reduction in noise in the electrical signal that I personally find exhibits itself as grain and hash that once removed results as richer timbre and improved liquidity, silence in backgrounds, and space evident between images.  I should probably add ground improvements to my next system upgrade.  

+1 for Bacch4Mac, but Edgar (the inventor) will tell you that you absolutely need to treat the first reflection points.  Best of luck.

I would do in order:

(1) dedicated lines

(2) Audiophile receptacles (Furutech GTX-D (Gold or Rhodium to your taste), Oyaide R-1, or for the budget minded Acme Audio Labs cryo silver

(3) Acoustic treatment, GIK Acoustics is an affordable place to start with free advice

(4) Better interconnects and speaker cables

I am not surprised that you are happy with your system!

Your KEFs are brilliant speakers, in part because they try to emulate a point source of sound by having the tweeter and midrange concentric. This means they throw a very wide soundstage, are much less critical of positioning than ’conventional’ dynamic speakers, and do not exhibit the severe comb-filtering that others correct with room treatments. For those who are new to these speakers, KEF has a truly excellent 40-page white paper which explores their design decisions.

There are a couple of upgrade options for the speakers. The obvious one is to replace them with the latest meta incarnation. In principle, meta is a small plastic tuned absorber disk that sits at the back of the tweeter. A myriad other changes were needed to accommodate the meta disk. While meta technology is very successful in KEFs smaller speakers, I think the Reference Series is so good that the benefits from meta are marginal.

The other option I’d suggest will be counter intuitive to most people on this site. It is to consider moving to the smaller Reference 1 speakers. All the Reference Series use the same concentric tweeter / midrange. The difference is in the number of bass drivers (which are all identical as well!). The Reference 1 has a single bass driver, the Reference 3 has two in a d’Apolito array, and the Reference 5 has four. The more bass drivers, the more likelihood there is for comb filtering, where the time delay in the different signal paths causes cancellation and reinforcement.

I have used Quad electrostatic speakers for about four decades so I am used to accurate sound. I recently added a pair of Reference 1 speakers (not meta) and I prefer them. They produce a staggering amount of quality volume and credible detail.

Your DAC has separate paths for Direct Stream Digital so one upgrade might be to buy a Super Audio Compact Disk transport, which I would recommend if you play much classical music.