I can only speak from my own experience here (and that's with one unit called "Gadmei TV3488E").
My unit doesn't work on CRT's, but the ones I linked to above seem to support both CRT and LCD screens.
As for the quality, I have only tested it on the C64DTV and regular TV signals, and the quality is quite OK. A little noise here and there, like what you would expect on a regular TV. I guess you get what you pay for, in my case $10.
Worth a try, IMO.