Wow, what a coincidence. I assume you like the VM-1a pairing better than the Krell pairing? It looks like the ultimate package.
The VM-1a and the CA-1a and SR1a are so amazing that I think they compete with $100K system (no physical room acoustics to deal with). There is no amp interface box needed to hook up the SR1a or CA-1a so you gain a tremendous advantage. I spent a lot of money and time making my SR1a sound great. Here are some of the final results.
Benchmark DAC3B | RAAL VM-1a | RAAL CA-1a + SR1a = a Spinal Tap 11/10. I cannot praise it enough. I had to move it out of my office system because I cannot work with this system. It is way too distracting. Things that should have taken me 30 minutes to do ended up taking 3 hours. So I moved the system to my second office/bedroom.
CODA 07x preamp | Musetec 005 DAC | KRELL Dou 175XD amp | RAAL SR1a + amp interface box = 8.5/10. I used to say this was a 9/10 but I downgraded it because there needs to be more separation with the VM-1a. I use this in my office which also has KEF LS50 Meta and Benchmark AHB2 mono amps. I sold the CODA 07x preamp 3 days ago and will be using the Benchmark LA4 preamp. The CODA 07x preamp is smoother and a bit better on the SR1a but I like the LA4 more on the KEF LS50 and it it still excellent on the SR1a. I can get work done with this system (late at night).
KRELL K-300i integrated | RAAL SR1a + amp interface box = 7.5/10. I used the internal DAC on the K-300i. An external DAC can boost this sound a bit more. On speakers this integrated amp is great.
RAAL HSA-1b headphone amp | RAAL SR1a | Benchmark DAC3B (did not have the Musetec 005 DAC then) = 7.5/10
Schitt Jotenhuim | SR1a + CA-1a | Topping D90LE DAC = 6/10. It is still enjoyable even though it is my worst setup.
The SR1a and CA-1a are not easy to get right with 2-channel gear. I had about 10 amps, 4 preamps, and 4 DACs on it. The very best combo is what I listed above. If you decide to use 2-channel gear then use something with a bit a warmth to tame the RAAL ribbon. For, example I could only make the Benchmark AHB2 monos work with them using the Schitt Freya+ tube preamp and Musetec 005 DAC (also slightly warm and smooth).
The 2 easiest ways to get great sound from the SR1a is the KRELL K-300i integrated and of course the RAAL VM-1a amp (with a bright DAC).
I hope this helps someone and piques their curiosity as to what the heck I am talking about. Stereophile will be getting the RAAL gear I have for a future review. I am now friends with Danny at RAAL so I am clued into some of their happenings.