Thank you to everyone for your responses.
Being the intrepid person I am my decisions were made before reading your posts.
My first purchase was the Questyle CAS192 MINI DAC (with the Wolfson WM8741). I couldn't afford both the CAS192 and the CMA800R so I went with the much cheaper option.
My initial experience was somewhat disappointing. I listen almost exclusively to classical music and to me the differences between the DX100 > Lehmann BCL and the DX100 > Mini DAC > BCL were subtle. For the most part I could readily attribute them to the placebo effect. However on specific pieces that highlighted the differences there was an obvious difference. For example Soler's Fandango in D Minor, a solo harpsichord work. Here the enhanced attack and solidity of the note was readily apparent and much preferred. However on most classical pieces this attribute wasn't readily apparent.
Then I added the CMA800R to the mix. Nothing subtle here. The DX100 > CAS192 Mini DAC > CMA800R is an impressive combination. The improvement over the BCL was more than I expected. There's more space around the instruments, the timbres are more clearly defined, the ambience of the venue is clearer, everything is clearer and more focused.
It's common to hear people mention hearing new things when listening after adding a piece of kit. With the new rig in some works I hear whole layers of sound that I hadn't been aware of. In some cases it has been startling. I attribute it to the Mini DACs/CMA800Rs abilility to resolve subtleties that get lost with other gear such as the BCL. These qualities aren't apparent with every recording. But on well recorded classical works with rich textures the differences can be striking.
Alden at Questyle mentioned to me that the CAS192 was preferred to the Mini DAC by a number of listeners who compared them. Perhaps at some point if I'm flush for cash I'll give it a try. Meanwhile I'm quite impressed with the Mini DAC/CMA800R combination and will continue to enjoy the wonderful music they make.
Edited by Omphalopsychite - 1/23/14 at 12:56am