Viridian, there is no doubt about source first; I'm an electronics tech, that's what I did until I retired. Source first is a fact from a "scientific" point of view. The preamp takes what you give it, makes it bigger, passes that to the amp, which gives it to the speaker. If you gave the pre "crap" it's going to give bigger "crap" to the amp which gives fat "crap" to the speaker; some people claim that fat crap sounds good if it comes out of the right speaker.
With cartridges your only option, since you can't audition the cartridge, is to pay careful attention to the music the reviewer is using. If he likes the cartridge when using the (same music) you like, that's a good bet.
I wont even mention the cartridge I like, because it gets bad press on most from this forum, and I can understand that because type of music determines the cartridge best for whoever is buying it. Relative to everything else, the front end is expensive, if it's to be a good one, even when you make it better with "tweaks", the good tweaks aren't cheap.
Sota Star Saphire is my favorite. 1K in tweaks can give you a Rega P-3 that will run with the big dogs, like the Sota Star Saphire; that's a big dog in my league any way; No Great Dane's in my league.
Enjoy the music.