I like the NT2a and the spc3, the 420 I have not heard. The spc3 sounds fantastic as a stereo pair, I made some wonderful recordings with it.
That said I would look for a used pair of AT4050's, or get two singles on ebay. AT claims any two 4050 will match... The 4050's might be the best sounding LDC I have every had the pleasure of working with, as far as diffuse field recording goes... You may also want to look at the ADK LD's....