cartridge output level

Yes, I now understand that you have 77 dB of gain prior to your power amp. That should be enough gain (77 db gain of 0.45 mV is a gain factor of almost 8,000, so your preamp output should be close to 3.2 V) which should be way enough gain for your power amp. Unless, of course, your power amp has low voltage gain, which I doubt, and/or your speakers have low voltage sensitivity. To get the dB from input and output voltages (output/input=gain) you use the formula dB=20 log (Vout/Vin). In your example your dB is 77, Vin is 0.45mV. If you solve for Vout you get 3.2 volts. This should be plenty of voltage to run your power amp to full power assuming it has a normal gain of 20-30 dB. Something does not add up here so maybe Hovland can shed some light on your problem. Let us know what they say. Again, I think you said it right, you probably have a voltage gain problem, not a cartridge output problem.

As an aside from the current discussion:
The Thor Cantantus has a fixed resistor that you can specify, is best for cartridges at .65mVolts but my Sumiko Celebration at .5mVolts works fine. My preamp lacks a phono preamp so it was necessary to get a separte piece.
Check and see if the SUT is in, a voltage reading should tell Hovland that info, let them instruct you just in case, working with live units is for people trained to do so.
As a former electronic tech, better safe than sorry

Rlawry, according to Marco's reports, he's getting ~0,9v at the output with the SUT in the circuit (63dB) -- before even hitting the active pre... and that's the reported overload ceiling of the phono.
Strange, as you & Marty note.

Rlawry, that formula made me think a lot, for example, based on that, if the SUTs were out of the circuit the total gain would be 60 dB (77-17), and the max preamp output 0.45 volts, so am I correct in ruling out this option?
I don't know the gain of my power amps, but I know that, in my room with my system, when I use the CD I'm happy with the volume at 12 o'clock. Now, this CD has an output of 2 volts, the line stage has 14 dB gain, that means according to the formula a max output from preamp of about 10 volts. Let's assume that, to make me happy, I need 3 volts out of the preamp, and that happens when the volume knob hits 12 o'clock in CD replay, it would make sense that, to get the same 3 volts in LP replay, I need to hit 3 o'clock, in the noisy area, being the max output from phono 3.2 volts as per your calculation.
Bottom line, to bring the voume back to 12 o'clock with LPs, I think I need to increase the voltage gain of the phono stage, just as you said, and to do so I only see 2 options:
1-Outboard phono stage with higher gain as you suggested, is your Rhea noisy @ 75 dB?
2-Cart with higher output level, a 0.6 mv one would give a max output of about 4.3 volts, would those be enough to bring the volume back a few clicks down?
Hmmm, decisions, decisions, life is hard...

I agree with your statement that your CD output of 2 volts will lead to about 10 volts output from your preamp using the linestage. But 3 volts output from your preamp should still be enough. The only thing I can think of is that the taper on your volume control is such that the gain is low until 12:00 or so and increases rapidly after that, but still, it should not be encountering much noise in your preamp unless the tubes themselves are noisy. I have never tried the 75 dB gain position in my Aesthetix Rhea, but even with 62 dB I had to buy some low-noise tubes from Upscale Audio to minimize tube rush because the phono stage uses tubes for all of the gain. One time a tube was going bad and causing big thumps through my speakers and subwoofer. Going to 0.65 mV will help, so that is a solution, but there are a lot of solid-state phono preamps that go above 60 dB. Again, I think Hovland should be able to help you.