Specific to CROFT phono users

I would never sacrifice detail and openness for warmth. I think the very nature of high fidelity demands we extract as much detail as possible. If the system is balanced and tuned, the warmth should be present by default. Harshness and distortion can present as brightness and false detail.

@fjn I should also note that your preference for warm (i.e. colored) sound indicated by preferring the JJs may mean you will be happy with less ultimate detail. I’m not sure. I know that when I changed my JJs out for Telefunkens, it was like I’d cleaned my windshield.

I have read good things about the Audionote/Goldring IQ3. For me, it's all about speed and detail and that is where the London(Decca)/Croft shines. Nothing you do in the chain afterwards can make that back. I've avoided adding another stage of gain. I have spoken to Glenn Croft on a number of occasions on the MM/MC debacle and his advice was to stay with the Decca. I run two rigs with 2 Crofts and have not been tempted to move to LOMC such is the awesomeness of the music it produces.

MM. Or a London Decca SG.
IIRC, this is your second system and you’ve been on the fence a while on this. For the standard Croft Integrated, I’d stick with the following:
1. Your upgraded BB tubes if you are happy with them. 
2. A new power cable.
3. Remove the lid if possible (sounds more "open")
4. A MM as many have suggested.

If you want to get into MC, then you might want separates like the Micro 25R phono and perhaps solder in a SUT.