、。
With rock music, it's difficult to say what criterion should count as hi-fi.
Literal
Rock [genitive-の] case, what [object-を] standard [to-に] hi-fi [quotative-とする][genitive-の] [subject-が] difficult is [confirmatory-ね].
A casual analytical comment in audio/hi-fi hobbyist register. The frame [noun]を基準に~とする ('treat X as the standard for Y,' 'use X as the criterion for Y') is a set pattern. Here it's a wh-indirect question: 何を基準にハイファイとするのか ('what should be the criterion for treating it as hi-fi?'). The か nominalizes the whole wh-clause. ~のか is then followed by が (the subject marker for 難しい). The sentence-final ですね invites agreement with a mildly reflective tone. ハイファイ (hi-fi, high fidelity) is a loanword from audio/technology vocabulary.