The Grado Statement 1 works best at 47K ohm.
The Hovland HP-100 could originally be fitted optionally with either the MM or MC phono stage, not both. You have the MC phono stage installed which loads at 450 ohm, which Hovland thought was ideal for most MC cartridges. If available, you could install the Hovland MM phono stage, or use an outboard MM phono stage capable of loading at 47K ohms through the AUX input. However, the Hovland MM phono stage loads at 1 megaohm, not 47K ohms. Not sure how that would sound with the Statement 1.
The Hovland HP-100 could originally be fitted optionally with either the MM or MC phono stage, not both. You have the MC phono stage installed which loads at 450 ohm, which Hovland thought was ideal for most MC cartridges. If available, you could install the Hovland MM phono stage, or use an outboard MM phono stage capable of loading at 47K ohms through the AUX input. However, the Hovland MM phono stage loads at 1 megaohm, not 47K ohms. Not sure how that would sound with the Statement 1.