Learn Italian: Quale stupore davanti a un capolavoro così antico! - What amazement in front of such an ancient masterpiece!

Yes, you can! In exclamative sentences, both Quale and Che can be used directly before a noun to mean "What a...". Quale stupore is slightly more elevated or poetic than Che stupore, but both are perfectly correct and mean the exact same thing here.

Why do we need the a in davanti a un capolavoro?

The word davanti (in front / ahead) is an adverb. When you want to link it to a noun to mean "in front of [something]", it must be paired with the preposition a. You cannot just say davanti un capolavoro.

The English translation says "such an ancient masterpiece". Why is the Italian word order un capolavoro così antico?

In English, we usually say "such an [adjective] [noun]". Italian takes a different approach, grouping the noun first followed by così (so) and the adjective. Literally, it structures the phrase as "a masterpiece so ancient": un capolavoro + così + antico.

Since capolavoro is a compound word, how would I make it plural if there were multiple masterpieces?