Cartridge suggestions

Practicability considerations:

Signal Strength, related amplification factors

I also use only MM; higher output a choice factor, I prefer at least 3.5mV.
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Calibration Skills (and related tools)

Skills and tools for many alignments/calibrations are VERY important for ANY TT, ANY Arm, ANY Cartridge. Expensive or Basic. A bargain setup can beat a very costly system depending on calibrations.  LP can beat CD, beat streaming, ... ONLY if properly setup!

Owner skills, or access to a professional for proper setup is important.
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Stylus Shape, Cantilever Material, Replacement

Think stylus shape, cantilever material, and cost/availability of replacement stylus now when choosing a cartridge.

highly respected source of replacement stylus

https://www.jico-stylus.com/

I prefer either Shibata or SAS stylus shape. I avoid the most brittle cantilever, thus I bought a replacement stylus: SAS stylus tip with Boron cantilever from Jico.

https://www.jico-stylus.com/product/vn5xmr-hg-sas-b/
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Cleaning Skills

Using advanced stylus shapes with more contact surface in the grooves makes cleaning even more important. Clean Stylus is important. People who experience lots of disruptive static most often lack the proper cleaning skills. I recently improved my cleaning skills, and am enjoying my used LPs with SAS tip essentially static free.

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Elliptical Stylus is Less Costly

Example: Shure m97xe. now discontinued (Shure stopped making cartridges). I used this quite happily for years. Jico makes a replacement stylus for it:

https://www.jico-stylus.com/product/n97xe-sas-b/comment-page-6/

Find one? Find a body and put a new Jico SAS stylus in it? (body you can return).
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Brushes

I like Shure brushes (and the sound of their cartridges).

Damped to steady LP irregularities, anti-static, and gathers small particles before the stylus gets to the grooves. Other brush arrangements exist.

Shure (others) with integral brushes can be used with the brush down in use, or pivoted up off the LP, Shure factory damped brushes, when down in use 'push up' 0.5g; so i.e. for 1.25g tracking force, using brush, set at 1.75 tracking, and anti-skate to match the 'effective 1.25 TF.

If set, and changing to brush up out of use, re calibrate TF to 1.25, double check anti-skate which was set for 1.25 already.

Jico wrote me that their replacement brushes are NOT damped, just a brush, so the upward force is different, a bit of guess work involved. 
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Protection of Stylus 

Check out the method/ease of stylus protection during detailed arm/cartridge/stylus calibrations.

Shure flip up/down brushes, Jico replacement stylus with flip up/down brush, and Audio Technica slip on protective cover are all easy.

My Grado Mono cartridge (love it's sound): it's small snap on plastic cover is ok for shipping, but lousy for protection when calibrating.
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USED

I would consider buying a used cartridge body, from a highly regarded source, only if returns accepted. 

I would plan on the cost of a replacement stylus in cost calculations.

Used Stylus, separate or comes in used cartridge body you want: that's risky, might get lucky, but 

Audio-Technica VM740ML or VM750SH.  About as good as MM gets (in my opinion) and fits the "neutral and articulate" brief perfectly.

Thanks for all this info! I had previously heard good things about the LP Gear cartridge, as well as some of the AT's. 

As far as set up, I have enough of the "stuff" required and have a "healthy" amount of OCD and understanding as to the process of properly setting up a cartridge. And yes, makes a huge difference!

I also like the Audio Technica ML Microline Cartridges, I have the AT440ml (earlier version)

this I consider a great find, NEW, BUY IT NOW, $192. delivered

https://www.ebay.com/itm/Audio-Technica-AT440MLb-Cartridge/202816707471?hash=item2f38d15b8f:g:VkgAAOSwtsBdw2Ui

no returns, but, says unopened, and protected by paypal/ebay, and, use your best credit card with protection.

'Quadrophonic' in description. Don't be confused, these are terrific for stereo. The advanced stylus, deeper in the groove, were needed for the short quad lp era. Actually, we have quad to thank for these advanced stylus shapes.

Buy a cartridge only from reputable brands who actually made them, not from the brands like LP Gear who does not make them, they often sells fake styli for well known cartridges (i’ve seen it many times and their styli does not look like my originals for certain cartridges, it was easy to compare them visually). LP gear is not the manufacturer. Most of the cartridge manufacturers are in Japan, so various brand just ordering their cartridges from Japan with their logo on it, but such brands does not design cartridges, they are not a cartridge designers. They are doing it just to make profit, not because they want to invent something new and interesting.

So if you want something interesting you have to look for well known brands in cartridge design, it can be American, Australian, German, Swiss or Japanese brands.

You could use an MC, but only with external SUT + MM phono stage (or with external Headamp + MM phono stage).

However, total cost of the nice MC with nice SUT is much higher than for a decent MM or MI cartridge. Also you can’t swap the stylus on MC cartridge (only re-tip).

Also spending much for a cartridge on this cheap lightweight plastic belt drive turntable is not a good idea, the tonearm does not have adjustments, it can be too complicated to adjust a cartridge on this cheap tonearm, you can’t even change the VTA as far as i know, so stay away from expensive cartridges.

The idea to look for MM is good idea.

But what is your budget ?

As you know many people prefer NOS tubes and they are almost always better than NEW modern tubes (i tried many). Same about most of the modern MM cartridges, for some reason they are not better than NOS vintage cartridge from the golden analog era (70s/80s) when MM was a king!

Few years ago i installed Stanton 881s mkII Stereohedron on the same turntable, i also did it for a friend. He was more than happy with Stanton 881s, the stock ortofom M2 Red sound like garbage in comparison with Stanton 881s which is not even the best Stanton from the golden era.

Read this article first, then you will understand why they are so good.

Pickering XSV/3000 is a twin brother of Stanton 881s, but for the Pro-Ject tonearm slightly lower compliance (mid compliance) would be even better, there was a special version of Pickering XSV/3000 with lower compliance (15cu instead of 30cu), that version was made since 1989 and it was Pickering XSV/3000SP. You will find more online. It’s not a problem to find NOS sample of XSV/3000, but the 3000SP is very hard to find, but it’s better match for Pro-Ject arm.

Over decades audiogon members shared personal experience about vintage MM cartridges, many people compared them to very expensive LOMC. Taking in count the price difference many a’gon member prefered vintage MM to expensive MC. You can find all information on audiogon. For me it was very interesting reading for a few years :))

Some of the top MM for moderate price are: Stanton 881s, Pickering XSV/3000 and 4000, Garrott P77, Victor X-1IIe, Grace F9, AT-ML150 OCC, Ganz 31L and Astatic MF200, Jeweltone or Nagaoka MP-50, Pioneer PC-1000 mkII ... and with a higher models from the same brands you can get absolutely the best MM cartridges, but for much higher price than vintage ones.