Responses from hk_fan

Router for Audio Streaming
Another TP-link mesh user and happy with it.  
Budget DAC recommendation for Office system
I'll second the MyDac.  I will likely be putting mine up for sale soon as I no longer have an office system so it's just resting in a box.  It's a great unit and a fabulous bargain IMO.    
Ayre KX-5 preamp with V-3 amp
I will echo the recommendation to upgrade your QB-9 to Twenty status.  I had mine done over a year ago and it's a significant upgrade.  I feed mine with a Lumin source and also have JC1 amps in the chain.  It all works extremely well together. 
What do audiophiles do in their cars?
I really enjoy high end car audio and am able to get very good imaging/performance with my DSP by fine tuning the speaker delays and freq responses.  I've spent quite a bit of time tuning it, but it's something that is a lot of fun. 
Are Pre-Amps necessary?
In my experience, yes they are needed to get the best out of your music. 
Class A into Class AB
My Parasound JC1's have a high bias mode which provides 25W of Class-A before switching to A/B, vs 10W in low bias mode.  It's clearly an audible improvement which I use when doing serious listening.  Not marketing fluff in my experience with the ... 
Integrated / speaker pairings in the $6-7K range
I had fantastic results with Focal Dome sub/sat system and a Micromega AS-400 integrated.   
Which subwoofer?
I've owned Velodyne, SVS and RBH subs - and now have a JL F112 V2.  The JL is in a completely different league in my system. 
A Word About SkyFi audio Customer Service
Totally agree ebm.  SkyFi is your place...  
Lumin or Aurender
I chose Lumin, very happy with it. 
Amp Upgrade time, $6000 budget, used or new.
There is a nice pair of Parasound JC1's listed for $4500.  I've had mine for years and have no desire to upgrade. 
What is Happening?
Is it possible you have some tubes that need to be replaced? 
Audioquest DBS System
Mine just died after probably 5 years or so, easy replacement. 
Need a preamp, new or used.
I have very similar musical tastes and also use Parasound amplification (JC1's) with AQ cabling and have been really happy with my Levinson 326 preamp.The rest of my system includes a Lumin streamer, Ayre QB-9 Twenty DAC, Aerial 10T's and a JL F11... 
Is the Mytek Brooklyn Bridge or Lumin D2 good buys in 2021?
Another vote for Lumin.  I'm using their U1 Mini to my Ayre QB-9 and thrilled with the combo.