Looking for a better preamp match for AT OC-9/III

Hello! I'm looking for a new preamp to use with my AT OC-9/III cartridge.

Currently I use a Graham Slee Graham Amp 3 Fanfare and here are some of the specs:

* MC with 0.2 - 1.0mV output.

* The input impedance is fixed at 470 ohms

Here is some info about my AT OC-9/III cartridge:

Type: Moving coil (MC)
Freq response: 15 to 50,000 Hz
Output voltage: 0.4mV (1 kHz, 5 cm/sec.)
Channel separation: 30 dB (1 kHz)
Channel balance: 0.5 dB (1 kHz)
Tracking force: 1.8 to 2.2 g (standard: 2.0 g)
Coil impedance: 12 Ω (1 kHz)
DC resistance: 12 Ω Min.
Recommended load impedance: 100 Ω (when head amplifier is connected)

I'm running the turntable as a desktop system and going out of the preamp into the aux input of a set of powered KEF LS50.

My issue:

This Graham Slee appears on paper (from my limited knowledge) to be a good pairing, but I always have to turn the amp very high to the point that I hear "air" and also a tiny bit of hum in order to listen at a decent volume. This behavior is exactly what I'd expect running an instrument (like a keyboard) into a mixer and not having the volume set high enough on the instrument and having to use the gain stage on a mixer to pump it up until it is super hot and introducing unwanted hiss.

Is this something common to all MC cartridges? I have had this cartridge on two different tables, two different amps, 3 different pre-amps, in 4 different houses, with different speakers, and currently have all new high-grade cables. I even sent the cartridge to AT to make sure it was good. They tested it and sent it back, saying it was within their specifications and I had it professionally installed. Is this gap in gain that I seem to be perceiving typical behavior from an MC setup? Apologies for my ignorance. I am really stuck on this cartridge and have a huge knowledge gap when it comes to phono audio.