I sold my CV 35 2.5 LTM in silver chrome, as well as the 50 3.5 Heliar earlier this year. I also sold my tiny silver CV 15 4.5 in LTM. I picked up a Summicron 35 ASPH in LTM and Summicron 50 (latest version) in LTM in the process. The Leicas are built more solidly than the CV lenses, but image wise, the CV gear was extremely good. In LTM, you can't get any better than these Leica lenses. They are the cat's meow for my IIIG. I also use them with adapters on my M7.
I regretted selling the CV 35 C - now discontinued. It took me a tortuous route through the Leica Summaron 35 3.5 LTM, Summaron 35 2.8 LTM, and Summicron 35 ASPH LTM to equal or better it. I've learned my lesson, and I'm not selling any of these lenses (yet), though they are redundant in the 35mm focal length. The Summaron 2.8 and Summicron ASPH are rare in LTM, so that explains my reluctance to ever let these go.
I regret the loss of the 50 3.5 Heliar LTM too, especially as you tend to lose money on these lens sales. It is an outstanding lens, and can compare with the latest version Summicron or the Elmar 2.8 M any day.
I regretted the loss of the CV 15 also, so I bought it back in M mount form. I also picked up a Zeiss 15mm finder in the deal. I'm not letting this one go away again.
After making these expensive sacrifices, the plus is that the Leica lenses hold up their value a lot better than most other lenses, and may even gain value with time. This is brought home to me when I look at ebay values of my manual focus Nikon AI, AIS lenses. The really good Nikon glass holds its value too, but not by as large a margin as Leica. Exceptions are the low production lenses, such as my 70-180 f/4.5 - 5.6 Micro Nikkor zoom, which have gained value tremendously. I bought mine new in 1996, not realizing that it was destined to become a limited production cult lens. I have no intention to sell it, as it is a great lens, and unbeatable in its convenience when taking macro images. It requires the Nikon doublet close-up lens 6T to achieve 1:1 magnification. So, I have the 5T and 6T lenses too. Now, Nikon has discontinued these lenses and they are stratospheric in price on the used market.
In your situation, I'd sell the CV 28 1.9 and one of the 50s, and swallow the bitter pill of financial loss on selling your CV glass. Then, purchase the Leica 28 ASPH M, and pay even more. But, in the end you'll be happy knowing that you have bought the finest that has ever been made. Until you do this, the question will keep nagging at you endlessly. I've been there, and gone through it, so I know. Suffer your pain now, and you'll be happier in the long run.
