I believe the importance of the "correct" load impedance for a LOMC cartridge is vastly overstated. Most manufacturers don't actually specify an optimum load impedance, just a
minimum load impedance. In the wider world of audio electronics it is considered normal that the load impedance should be much higher than the source impedance - the source impedance being the resistance of the cartridge's coils in this case. A factor of 1:10 is usually considered high enough, and with most LOMCs having a coil resistance of approximately 10 ohms a load impedance of 100 ohms satisfies that 1:10 rule. Coils also have inductance as well as resistance but the inductance is usually so low in an LOMC that it is negligible.
I find I prefer the results I get using a quality SUT and the phono on its lowest gain settings and loading on 47k.
Yes, many people have found the same. I'm only surprised that there aren't more people using the SUT-plus-mm phonostage option.
My main cartridge (Monster Alpha 2) should be loaded at about 20-40 ohms, so I rigged up a way to put a resistor across (in parallel) with the cartridge coil on the output of my turntable. After much experimentation I decided that it sounds virtually identical with a 100 ohm load (via the phono pre) as it does when adding a resistor to bring the "load" down to roughly 30 ohms.
I think many manufacturers specify a load impedance for their cartridges because people expect to see that kind of information and they don't want to say "it doesn't really matter that much". The manufacturers who specify only a minimum impedance come close to admitting it doesn't really matter that much.
I'm not surprised your cartridge sounds identical with 30 ohm loading and 100 ohm loading.
I have one cart with a very annoying peaky treble. I have a tube phono-only preamp lets me load it down as low as 10 ohms, and that fixes the treble — but everything else suffers.
Yes, when the load impedance gets down really low - say less than 3x the coil impedance - the overall output will drop but maybe the treble will drop a bit more than everything else. Possibly better than a low resistance load would be a high capacitance load. There's thread about just that here on the forum.
http://audiokarma.org/forums/index.php?threads/lomc-treble-peak-capacitor-cure.838117/
Of course, you already know about that thread - you started it
Anyway, to answer the OP, I don't think you're missing out on very much.