Concerned about my cart/pre pairing

There is additional information here on cartridge/SUT matching


https://www.vinylengine.com/tools.shtml

There is no advantage to using a high gain stage with a lomc cartridge because all such active stages add noise - something to be avoided! Properly amplified a lomc cartridge has a significantly lower noise floor than any mm or mi cartridge. A transformer is the best way to convert the high current of a lomc to the higher voltage required by a phono stage - all without adding more noise!

The only caveats regarding an SUT is that it must be grounded to the tonearm/TT AND the phono stage/preamp. 2: The IC from the SUT to the phono stage/preamp should be kept as short as possible. This is to avoid high frequency roll-off due to capacitive loading between the transformer secondary winding and the connecting cable. The interconnect cable between the lomc cartridge and SUT can be any reasonable length. A meter or two or three doesn't have any deleterious effect.

To be honest, a high gain phono stage for 0.3 mV cartridge is not necessary, a high gain phono stage is required for 0.05 mV or 0.15 mV cartridges and those very low output carts can be problematic even with SUT, Headamp or phono stage.

Personally I use all methods including current-injection type of the phono stage for low impedance cartridges.

I can’t categorically say that SUT is the best!

But MM/MI carts are dead quiet almost with every good phono stage, the MC are not.

Despite the many self-assured responses you received, no one can really analyze the phono gain inherent in your system without also knowing something about your amplifier and speakers.  First, the SPLs coming from your system depend not only upon the output from your preamp but also on the input sensitivity of your amplifier.  Input sensitivity is defined as the signal voltage required to drive your amp to its full output.  Typically that is anywhere from 0.5V to 2.0V, somewhere in there.  After that, we need to know the efficiency of your speakers and the size of your listening room.
But we can say that a cartridge that puts out 0.3mV into a phono stage with 58db of gain will result in a signal voltage of around 0.24V at the output of the phono section.  Bear in mind that the figure of 0.3mV is published by the manufacturer for a stylus velocity of either 3.54 or 5.0 cm/sec. Most music will actually push the stylus around a bit faster than the standard velocity; thus usually the rated output is a bit pessimistic as far as the actual overall gain you get.  Then that signal will go through the linestage of your preamplifier, which according to data posted by Chakster, adds 7db of gain, for a total signal voltage of about 0.5V.  Depending upon the input sensitivity of your amplifier, that might be close to enough if not quite enough to make your listening experience a happy one.  (To make these conversions of db to V, I use calculators available to anyone on-line.  You should learn to use them too.)
I don't at all agree with the insistence of a few that a SUT is always superior to a high gain phono stage, but if you do choose a SUT, you MUST connect it to the MM input of your phono stage, which we know yields 43db of gain.  The difference between your high and low gain inputs is therefore 15db. 15db of gain is equivalent to a voltage gain difference of 5.6X.  You want a SUT that adds more voltage gain than that, because you already know (pending further info about your amp and speakers) that 58db is not enough.  Your cartridge, which has an internal resistance of 5 ohms, according to someone, will work fine with a SUT that has a 1:20 turns ratio (a voltage gain of 20X).  That combo of 43db gain from your MM stage plus a SUT with a 1:20 turns ratio should put you in a safe area for total gain.  1:10 might work too (voltage gain 10X).
I think why many others think 58db should be "enough" is because most linestage sections add more than 7db of gain on top of the output of the phono section, more typically 10 to 20db.  That may be why the consensus is you should have enough gain already.  Plus we don't know about your amplifier.