educate me

If you go for an MC cart you want low output, unless your phono stage has only MM input. A good MC cart costs a lot, costs more than a good MM, but it will have much better response in the high frequencies. IMHO there's little point putting an MC cart on an entry-level tone arm, or in sending its signal to average electronics. The upgrade sequence usually recommended is 1. turntable 2. tone arm 3. cartridge 4. phono stage. There are exceptions and YMMV but that's as much of a nutshell as I can put an answer in.

I used my first LOMC in a Linn LP12 Lingo with a rewired Rega RB300 arm. If I had the same table today, without the Lingo or the LOMC, and I were hesitating before deciding on which of these to get, I would get the Lingo power supply before the cart. Hope this helps.

Even if you have Bose speakers, you will hear better sound from a better cartridge.

This is true, I think. One seriously interesting way to spend a budget is to put 80% of it into the source, then upgrade downstream as savings permit.

So I agree it might make some sense to listen to a great cartridge with Brand X speakers, if you hoped to upgrade eventually. The upgrade would only let you hear more of what the cartridge was already doing (but inaudibly) with those Brand X speakers. You have the highest-resolution component upstream. All systems should be balanced like this.

That's why it doesn't make sense to use a premium cartridge with an entry-level arm (and/or turntable). To put it one way, the cartridge's great resolution would let you hear the arm's limits much more clearly. Put another way, you would not be getting the best performance for the money you spent on the cartridge; whereas if you spent the money on upgrading the arm, you would then be getting more out of the cart.