Nady's generally considered hit or miss. Quality control issues have dogged them, but if you get a good one - it's a good one. I have a TCM1050 tube mic and my friend is a Nady dealer. We opened a few boxes and we found one with a microphonic tube, but they all generally sounded the same. Pretty decent for the money.
I put a NOS GE 5 Star 6072 in mine and found that it improved the performance of the mic. It was certainly quieter and smoother. We prefered the sound of the Nady on a male vocal over a Lawson U47 copy. It was not as open sounding or complex as the Lawson, but it had a warmth that the song needed.