Phono preamp worth it with MM cartridges?

Roger,
a good phono stage makes an improvement with either a MM or LOMC cart.

There are quite a few good ones out there, just depends on how deep you want to go into the woods. In the sub 2k range look for a used Manley Chinook. Does very well with both MC and MM carts. Have owned two of them over the years, you can pick one up used for 1400 to 1700 range.
The latest model has a switcher power supply so would avoid that, all the earlier models have a big fat toroid in the power supply section, which is what you want.  

I have personal experience with the elex-r built in phonostage as well as a rega p2 with the exact. The exact in all honesty had more "attack" than when I moved up to my Clearaudio Concept Wood table and the entry level Concept MM cartridge. I will go ahead and call the concept MM cartridge junk. Detail was improved, but everything else it offered was a step backwards. I accidentally broke the cantilever after too many drinks one night, which lead me to the sub $500 Hana EH which is a high output MC cartridge and I could not be happier.

Also, the Elex-r phonostage isn’t great, but it is decent. I moved to the Musical Surroundings Nova III and this phonostage is superb. I almost went Lehmann Black Cube but no local dealers stocked it. Michael Yee and Musical Surroundings have phonemal phonostages and even offer the option to add a liner power supply. This added even more "Identity" to the phono. I can highly recommend even calling Musical Surroundings as they have someone named Ken (I believe?) That you can talk to and won’t BS you into buying their products.

All in all, get rid of the exact, avoid the entry level Clearaudio MM and pick up either the Phenomena or the Nova III and don’t look back. That’s what I did.

Chak, To be clear, I was only questioning the "30"; you left out the "K".  I now see how you meant it.  Of course I do agree that for some MM cartridges 30K might work fine or even optimally, but not 30 ohms ever for any MM cartridge.  I just did not want the OP or anyone else to be confused.
On the subject of Clearaudio MM cartridges, some of them are excellent but at least one of the best is just a re-branded and externally altered version of a less expensive MM made by a main line Japanese company. Do some research on that, and you can save a significant fraction of cost.  I don't know if this applies to more than one of their MMs.

@lewm MM cartridge manufacturers in the 80’s clearly stated 30k - 100k Ohm range for their best (top of the line MM) in the manuals. Why?

Now it’s just 47k

Flexibility is a range, so user can try what’s the best.

@mijostyn You don’t have any of the best MM or MI from the past and never owned any of them, I don’t know what can I say ... You must try! If you wish you can try not MM junk like your old Shure V15 MK-whatever, but a proper $1500-3000 MM. I never said MM is better than MC and I own some of the best LOMC ever made too (and I like them). Do you have some? Please post. If you think cartridges getting better and better every years you’re wrong. The problem with LOMC is the price, repair/retip is nonsense. MM are practically better and best vintage MM are cheaper and often better than most of the modern MC.

Modern MMs are junk because the cantilever and styli are always the same (from the same jewel manufacturers in Japan). Nearly all of them are nothing special. Maybe 5% is an exception, but not what you guys are posting here, not a Nagaoka, not Ortofon and not a ClearAudio with dirt cheap Audio-Technica motor inside.

SoudSmith cartridges are not MM, they are MI and it’s another story.

If you like expensive stuff buy this one.
Prepare to spend over $10 000 for this, it’s NOT an MC.
Then tell us how do you like MI or MM :)  

Chak, I hope you understand that I am agreeing with you about 30K ohms.  Got that?  I personally have found most often that 100K ohms sounds best with many of my MMs.  This started with the Grado TLZ or XTZ which I know we both like. The TLZ sounded best with 100K ohms load.  I have actually never tried less than 47K ohms.  Also, in many cases it's a trade-off with capacitance.  If you increase R above 47K there would be a corresponding change in the best capacitative load.  If you don't want to mess around with C, you can just play with R (more or less) until you get the best result with whatever is the total C load seen by the phono stage.  You don't even have to know exactly the value of C, just change R until you are happy.