What should I expect moving from MM to MC?

@SecretGuy "High output MC really diminishes the supposed advantages of the MC design.

I'd probably keep saving to get a nice phono stage and low output MC."

Care to explain the reasons?

Personally I love my Sumiko Blue Point #2 MC cartridge.  Seems to give an extra ooomph to the base and very crisp highs. Plus I don’t use an expensive phono stage. 

While I've never been "tested", I have very sensitive ears and believe I can pick up frequencies over 20khz. 

That is fairly easy to test: 

MC carts are just faster - by design. Less mass with the same suspension results in faster transients. High output MC’s have slightly more mass (coils of wire), but not nearly as much as a magnet. I have never done a 1:1 compare low to high output. I suspect most of us would be hard pressed to identify a difference. I stick with low   outputs - just because. Your music choice may change how much of this makes it through. Punk and lo-fi doesn’t always benefit. Complex music as well as stripped down music does benefit. That being said I think you made the right choice. Start with the stand alone phono stage and go from there.
 

Quick note - I’m not familiar with the phono you selected, but some phono stages still struggle with hum at 65db gain. Before selecting a low MC, you may want to dial up the gain on your new phono (no music playing) and double the volume at your amp. If you get noise, dial back the gain at the phono till it goes away. Try moving it around as well. Compare against noise in the system going into the phono inputs without the preamp. Once you know what gain is acceptable, you should be able to select an appropriate MC cart. Also, look into resistance loading - that can change the sound as well. For MC’s, having an input resistance that is10x the internal resistance of the cartridge is a good rule of thumb. This is almost as important as gain, but harder to detect. Most systems have more gain than needed. MC’s running wide open (47k) loose their body and sound thin, generally speaking. 

warmer and fuller are not necessarily what lomc carts bring to the table.  you will get a cleaner, more refined sound which is abig step up in quality from most mm cartridges. also because of the lower moving mass an mc is typically more dynamic and full of life and musical energy.  think huge crescendos and fast musical transitions.  

many people who want warmer and fuller sound have system issues to fix and are trying to mask a lack of refinement.  start with perfecting your speaker positioning.