I think it's very critical. Two points to keep in mind...the cartridge has to like what it "sees" at the phono stage input, and the phono stage output has to be compatible with the line stage input.
The first point is most critical, input impedance and capacitance isn't for the phono stage's benefit, it's for the benefit of the cartridge. This is so for MM, MI and MC cartridges. Wrong setting and the cartridge may seem to "ring" because there's a peak in it's response. In other words, the frequency response is not flat because the cartridge is also acting like an inductor.
MM and MI cartridges for example like to see 47,000 ohm at the phono stage input, MC's like to see much, much less. Therefore, using a LOMI cartridge on a phono stage set for MC gain and typical MC load and capacitance will not sound the same as if that LOMI cartridge was used with a higher gain MM phono stage.
It is for this reason that I believe no single phono stage fits all situations. "My phono stage sounds great on my system, but not so good on a friend's" sort of thing, and vice versa.
I spent yesterday afternoon auditioning four different phono stages on a friend's system. The results on his system were very different than the results on my system. The only major differences between our systems were the cartridges (MC vs MI with similar output) and amount of line stage gain. Fine tuning the loading and capacitance on each system was necessary to attain the best sound for each situation.
They all work, one way or another. But if you want to get the most out of your vinyl, it seems proper matching and fine tuning is necessary. If the cartridge doesn't like what it sees, the sound may be splashy or boomy.
