The purpose of a preamp such as the Aurorasound EQ-100 is to playback discs using a pre-emphasis equalization other than the RIAA standard adopted around 1960 or so. If your collection includes original discs from early in the micro-groove LP and 45 era, then some of them may use EQ curves such as AES, Columbia, London, etc. All would be mono, of course.
Note that these early EQs only apply to the original discs mastered and pressed before ~1960. Reissues since that time would all use RIAA.
I have a second system based around an HK Citation preamp that supports these earlier EQs. I have one turntable set-up for 78 playback as well as another turntable for 45/LPs with a swapable mono or stereo cartridge.
My experience is that the old EQs are critical for playing 78s, but more subtle with LP/45s. Most of the early LPs I have with alternate EQs sound OK played back through RIAA. I’ve learned to listen for the difference. Getting the bass turnover correct removes an unnatural thickness/thinness in the lower mid/upper bass range. The correct high frequency roll-off gets the right balance of extension and surface noise reduction. But a casual listen might not notice anything amiss.
So, if you have a number of early LPs/45s in your collection, you might enjoy a preamp like the Aurorasound EQ-100 or other with similar flexible EQ to dial in the correct playback response.
BTW, I am considering adding a turntable with two tonearms to my main system with one dedicated to mono connected to a flexible EQ preamp. Good idea!