For a stand alone:
elegant: of high grade or quality
eloquent: marked by forceful and fluent expression

Both represent the new amp, so combined we have:
Axiom Elequant Digital Amp ED14.8
Axiom Elogant Digital Amp ED14.8

For a series:
elegance: refined grace or dignified propriety
eloquence: the quality of forceful and persuasive expressiveness

Combined:
Axiom Elequance Digital Amp Series (ED14.8 this model)
Axiom Elogance Digital Amp Series (ED14.8 this model)

Elegant and elegance obviously refer to its clean, minimalistic yet stalwart styling while eloquent and eloquence refer to the the way it provides its smooth, clean unrelenting power.