What should I expect moving from MM to MC?

Analog LP is a pain.  I advise you spend equal amounts on your phono preamp and cartridge as your TT.  Used market cut that in half.  MC LO vs HO MC the LO Output will pick up more Suttle details such as string vibration and tones in wood instruments sound right. HO is not a bad either. HO Chamber echos sound good and the recording should sound as intended with less noise pickup.  Price usually dictates quality.  As far as jump from MM to MC I would probably say price is more important across the entire chain.   Everything matters and you need to learn a lot have fun.  Its best to learn setup and what is going on yourself.  My Analog was less quality then Tube DAQ.  But after learning applying and just keep working with what I have now Analog is better.   Things may take longer then you think.  Its always good to notice quality within the few hours things sound good then it may take months to finally realize what the capabilities are.

+1 for what @alvinnir2 has written.

The way I would put it is that the movement to a MC cartridge would be expected to give you more of what we used to call low level information. That translates principally to things not available in the specification of a cartridge. The include space, instrumental articulation, & solidity or roundness of the instrumental sound. These things all contribute to the sense of being there in the recording. That would be the good news.

The not so good news IMO is that a high output MC is not likely to provide these benefits because the stylus, like that in MM cartridges, is just carrying too much weight at the other end. Also, you might also have to invest more in the rest of your system to fully appreciate these improvements.

I pay very little attention to reviews. They are just there to sell. Consensus opinions of actual purchasers, as fond in places like this have never failed me. It takes a bit longer to figure out but it pays in the long run. Not like the quick fix of a review.

Although there was a brief discussion of >20khz response, the OP has repeatedly prioritized a "fuller, warmer sound".  This sounds to me like the mid-range.

The original holder of the MC patent was audio legend Joe Grado.  However, he didn't make them.  A believer in the importance of getting the mid-range right, his cartridges were MI (Moving Iron).  AFAIK, Grado & Soundsmith are the major MI cartridge makers today.

The Schiit Mani 2 gives you plenty of versatility for optimizing your phono sound, and should result in meaningful improvement.  Upgrading your cartridge will cost more, but should also make a bigger difference in the sound.

Check out the Soundsmith web page he has plenty of info on different kinds of cartridges.

@ronald_p Great point about the used market. Definitely  a way to upgrade and save some money at the same time.

Mani 2 has arrived and works as advertised. I'm going through my albums on different eras and genres. So far I wall say there are notable differences, including the ones I was hoping for: broader soundstage and a boost in the previously flat mid-range frequencies. Vocals and solo instruments have come forward and the oomph of the bass with the fuller mid range have filled in the gaps. Thank you all for the recommendations.

I'll still go through a re-listen to most of my collection. Two albums that I love but just didn't sound right were:

1. Asia (Asia): Their debut album from 1982 was one of my all time favorites. I've listened to it  several hundred times over multiple medias over the years. The vocals and drums seemed distant and small. The Mani-2 has brought them back to life.
2. Stan Meets Chet (1958 Sten Getz / Chet Baker). Listening to an album that's nearly 65 years old and sounds lively and full is amazing when you really think about it. 
3. The song "Sound of Silence" by Simon and Garfunkel. With the more forward vocals, it's much fuller and the harmony of the two vocalists is appreciated more than I had previously
4. "Casbah" on the Rich vs Roach album. The Mani-2 really makes this vintage song come to life. I think partially my Klipsch horns highlight the brass, but he Mani-2 brings them to life.  
5. Round Midnight (Miles Davis) - This is my current Nirvana...until I move the goal posts again.

At some point I'd like to upgrade to a MC cartridge just to hear "what's next" in my sound journey, but the urgency has gone away, as the phono-amp has pushed this back. In a small 12 x 12 office with not-so-optimal acoustics, the sound is terrific right where I have it. 

So thanks again everyone!