Never tested myself, I can imagine that, on short distances, a Cat 5 Type S/UTP (Screened / Unshielded Twisted
Pair) or even an U/UTP (Unshielded / Unshielded Twisted Pair) might be sufficient to replace ML-cables (not PL-Cables).
But, if it's a very small "audio only" system and there are no plans to add/change components for a long time -
installing a proven ML could still be a simple alternative!
If this is not the case:
ONLY a CAT7 Cable Type S/FTP (Screened + Foiled Twisted Pair = separately foil-shielded twisted pairs and an
additional screenning of the complete cable) will be able to fulfill today's requierements in (analog) ML and PL
networks and will be able to offer sufficient bandwidth for future (digital) apps like streaming HD-video.
For sure, as a replacment for today's ML/PL a CAT5 or CAT6 of the same (S/FTP) type will work as well as a Cat7
but will hardly, if at all, be cheaper than CAT7 - you have to compare like with like !!
Even if you'll save a little bit of mony you surely will be loosing resources needed in the future.
PS:
Having installed miles/kilometers of ML /PL /CAT cables ... the amount for the
cables by meter was always a fraction of the total costs of the installation.
!! Don't shoot yourself in the foot !!