CC resistors will only have a clearly noticable effect when there is much voltage drop across the resistor - something which will lead to second order distortion. this means that you can use CCs for the slope resistor and the 100k plate resistors. also the 27k nfb resistor is notable. personally, I dont like 100k CCs resistors as it messes with the open ac/dc sound. This means that most of the CCs I use won't make a very noticable difference.
one of the reasons marshall used CCs was because of its long legs. e.g., the cathode resistors were CCs. I've tried to reflect this in my builds (except the power supply where I want stability). earliere marshalls used more CCs than the later plexis, for instance in the case of the 270k mixer resistors. I've also used more CCs in the 66 jtm than the 67.
a jtm45/100 sounds like a bigger and punchier jtm45. also its a bit more chimy and clean and it cleans up better
