Exactly they are a V8 brand, AMG is synonymous with the V8. An inline 6 as the top dog would still not feel right, That’s BMW.
The C32 AMG W203 is a sleeper cult classic. A mighty I6 would do just fine, and knowing MB it'll do bigger numbers than the next M3 so closing in on 600 hp.
It's actually pretty even in terms of V8 vs 6 cylinder in the C class, but yeah the V8 seems to have more presence:
W201: 6 cylinder (they made the C43 and C55 with V8, but rare)
W202: 6 cylinder (facelift did indeed become a V8)
W204: 8 cylinder
W205: 8 cylinder
Not disagreeing that AMG is synonymous with a big V8, but the C class would do just fine with a strong I6.