Speaking as one evaluating/peddling such things, at the time -
Garrard was ~ mass-market Plymouth 4dr. sedan of the changers. A few higher-end were produced, none of lasting significance IIRC.
Dual a decided step^ - as changers go/went.
But audio-fidelity was all about turntables, particular arms, and very-particularly about cartridges: then as now.
Many early changers had 78-45-33 settings, as did a few turntables (even there were a few 16 rpm narration discs! + a few of the above with that setting. I never saw a 16 disc.)
Today, probably best bet to audition 78s is some turntable. (A few 78s were produced with good equipment on vinyl, as were some later 78s of contemporary performances - for audiophiles.) These are no more 'obsolete' right now than, say: an original Toscanini recording is, or will be in 2056.
Changers won't accommodate decent modern cartridges (though a Dual would handle near-decent, in the day.) Many cartridges had optional 3-mil stylii available; elliptically shaped were ~ best. These are likely hard to run down, now. Dunno what specialty shops have come up with lately. I don't play in the fields of, especially today's Mondo-$$$ equipment for the obsessed 1% ... wanna see an ad for a $40K turntable?
Many (most?) 78 recordings were never rereleased on 78 or 33 vinyl; the artists being very-daid. ie treasures will remain Out There for some time, unless the land-fill reaches the inheritor before a collector can hear, bid, enjoy.. gloat over find.
PS - wash the records! if you do acquire a player. Use lukewarm water, some detergent and a new paintbrush (semi-stiff == not sable fine grade!) and brush in 'plow' mode. Lots of fine debris will come out. Rinsing: at least distilled water final rinse; best of all - 'deionized water' (favored too, by Yuppies washing their Meguiar-waxed $60K parked icons, each Saturday.) Dry in dish rack or via warm air blower.
(I have some Caruso, Amelita Galli-Curci, Jussi Bj\ufffdrling et al. Alas my \ufffdber-grade Linn-Sondek turntable may or may not adapt for 78; I have no 78 stylus-equipped cartridge, either. Yet.) Not high on list, as none of my copies is of a rarity.. Til the remaining stuff really IS trashed wholesale(?)
Someday, if there are many survivors of the Nuke Age - they will despise us for the art we trashed, during this period of retro-knownothingism (as they will despise the hucksters who sold the idea that 'the new' is always better aka So Buy-new! Land-fill the old! - to demonstrate your Cla$$ to the neighbors.)
ie recently I was watching Born Yesterday, Billie Holliday's magnum opus of the Smart dumb-blonde VS Broderick Crawford's Junk-bizness man of another era - his worst characteristics are found today in a few, on every Bored of Directors. Ugly prescience, in 1952?