MC Cartridge: Elliptical; around 0.5mv; track 1.25-1.75; Affordable

specs of that Denon 301 seem right in my range

Full specs:
Format: moving coil type
Output voltage: 0.3mV (1kHz 5cm / s in the horizontal direction)
Playback frequency range: 20Hz ~ 60kHz (the graph in the Gramophone review on vinylengine showed it to be dead flat to within about ±1dB up to 45kHz, the maximum frequency they tested it to)
40Ω: output impedance
Matched load: 100Ω or more (transformer 40Ω)
Channel separation: 28dB or more (1kHz)
Channel balance: 1dB or less (1kHz)
Static compliance: 35 × 10 (to the power of) -6cm/dyne
Dynamic compliance: 13 × 10-6cm/dyne (100Hz record measurement)
Needle tip: 0.14 × 0.07 mm square solid diamond special ellipse needle
Proper stylus force: 1.4g ± 0.2g

good first step into MC?

At your budget the Denon DL-301 MKII is a good value. 

It might help if you gave a little more information about your system.  If it's not that resolving, you might not notice a big difference between the carts you have, if it's highly resolving, it might point out some of the shortcomings of the DL-301 MKII.

You should notice more detail and a smoother presentation and probably improved bass with the Denon compared to the Shure.  I have no experience with the AT440ml.

If you really want to get into MC, I'd suggest saving up and get a Hana SL, it's noticeably better than the Denon, but the Denon is a nice way to dip your feet in the water.

I was reading about that Hana, made me want to click 'add to cart', but not that much money 'yet'. not until I hear some magic beyond my beloved Shure/Jico SAS

I like the Denon DL-301II more as I read users comments all over the web, and it fits my desired output at .4mv and light tracking force range 1.2-1.6g

new via ebay, $300.
https://www.ebay.com/itm/274398854460

Somewhere up this thread I read that your phono stage has a fixed input resistance of 100 ohms . Then I read that the Dynavector 301 has an internal resistance of 40 ohms. If both of those numbers are correct, and if you absolutely cannot change the input resistance of your phono stage, then this match is a no go. you want the input impedance of the phono stage to be about 10 times that of the internal resistance of the cartridge. This is a basic rule that you should commit to memory. It can be “bent” at the cartridge to phono stage interface but not by that much.What you would hear in this case is a dull sound and an apparent loss of gain.

I'm not sure how to quantify the difference, but the Denon will be somewhat similar in some ways and better in others than what you have.  The Hana will be clearly better than the Denon or anything you currently have.  The Denon will be a somewhat lateral move and give you a taste of what MC is about, the Hana will be a noticeable upgrade (dependent on your equipment's resolving ability).