mundorf m-resist supreme vs jantzen mox and others

The Mills MRA12 are the most accurate and neutral resistors I have tried. They are less HOT than Mundorf in terms of upper mids and highs. The Mills are quite natural sounding. 

The Duelund resistors are also good, but the CAST resistors can be a tad bright sounding in some systems. 

As usual this is always system dependent. 

 Mills MRA are better sounding to my ears.

I don't think warm is the right term, but I would say more fidelity to the recording. 

I really cannot speak to the bass. But the Mundorf is not as warm or dark as you say. The Mundorf has some added energy in the upper mids and highs in my estimation compared to the more neutral Mills MRA. The Mills is warmer compared to Mundorf in direct comparison.   That has been my experience. You can do a search and see what others think. 

Both image fine. 

Sorry been tied up.....Fidelity is actually the perfect word and what high fidelity audio is all about. Here is the definition: "the degree of exactness with which something is copied or reproduced" So a component higher in fidelity is truer to the source, musical event, actual sound of the instrument or voice etc....

They sound more real and deliver more high fidelity. Horns sound more as they should etc... Hope this helps. 

There you go! This question is very system dependent as well as subjective preferences. I will help you directionally however by saying the Mills are warmer and the Munforfs are more turned up in the brilliance area. You know your own preferences and system personality so plan accordingly. 

I really can't say as I have used these mostly on high pass boards. 

More Burn in time needed. Different room, speakers, gear, ears etc... all play a role. 

Yes, they both will change over time. Resistors certainly change over initial burn in time of say 60 hours...