Help me spend $$$$

@abd1 The CODA 5.5 was an amp that I was recently wondering how it would sound with the SR1a. Now in the olden days you needed about 100 watts of 2-channel power to drive the SR1a. However, today 20 watts maybe the max. Your 5.5 maybe too powerful for the new adapter and not enough for the old adapter. You can also drive it with things like a Schiit Mjolnir v3 Class A headphone amp using my adapter. You can get that used around $850. It is about 2 watts. 

The old amp adapter was not as good as the new one and it needed min 100 watts to drive the SR1a nicely. The next iteration was the Tl-1a | TI-1b | Tl-1c. I have the Tl-1b. They do not make that anymore, but you can get the latest one that works with the $12k RAAL 1995 Immanis to work with the SR1a.

The SR1a is the closest thing to 2-channel. The combo of the Imersiv D-1 DAC | Aegir v1 | Ti-1b adapter | SR1a is hard to beat. Especially from a 2-channel perspective. The SR1a scales with better gear.

Not familiar with the Audio GD stuff but may be good, and Schiit is worth a look too.  Of the others listed I’d take the Aune as they make well-regarded budget headphone gear.  If you can fit them I’d get these, which is the big brother Class A amp in the Aune family and a nice R2R DAC I actually own (you’d wanna run balanced interconnects between this amp and DAC BTW as the DAC — and probably the amp as well — sounds best that way).  I believe this pair would probably significantly outperform any of the combo units if it may work for you size wise, and it affords more flexibility if you wanna upgrade either in the future.  Hope this helps, and best of luck. 

https://www.usaudiomart.com/details/650273627-aune-s17-pro-shipping-included/

https://www.ebay.com/itm/187918828057

If you buy anything but Schiit, you'll spend much more for the same quality. No distributors to deal with so they can sell at a lower cost but with outstanding sound quality. 

I am in a similar boat as you. My wife and I are now sharing our office and I had my speaker system in the office. I’ve sold off most of my speaker gear and have upgraded my headphone system. I started focusing on headphones a few years ago and have tried quite a few headphones, headphone amps, and a few DAC’s. Currently was just able to upgrade to a fabulous Woo WA5-LE.

For what you are looking for, I would consider a Chord 2Qute or Denafrip Ares DAC and pair it with a LTA MZ2 headphone amp. I’ve worked my way up the LTA line and they are excellent. The way the tube circuit works, it doesn’t put off a lot of heat. The Chord 2Qute is small for your desktop and if I remember correctly it will function as a Roon endpoint even though it’s not officially listed. 

Another option if you want to stay in the Bluesound ecosystem and a lower budget would be to get a Hub or Nano and then pair it with a device like the Fiio K13 R2R. 

I have not heard the Schiit Mjolnir 3, but it gets very good reviews. It is quite large, but Schiit just came out with what is considered it’s baby brother in the Asgard X.  You can even get it with a Mesh DAC card. 

One other product that I just picked and am quite impressed with is the Cayin RU9. 

Regarding headphones, if you like open planars, you might check out Sash Tres. Two more you might put on your radar are the new HEDD D1 and ZMF.

Good luck with your search.

The Gustard Audalytic AH90 seems like the perfect device for you. 1 watt of power at 32 ohms should be enough for 99% of the headphones out there.  Balanced inputs and outputs.  Roon Bridge installed.  A nice DAC chip.  $600

https://headfonics.com/audalytic-ah90-review/