Well that totally depends on your requirements/goals, but I'd probably suggest to run Mellanox on the other side too.
CX4's are not that expensive any more and neither are 3m DACs if you're lucky.
I probably could spare some, but would need to take stock first since I just moved my core switch to 100G and need a few myself
Re noise - I have not tried replacing the fans inside, but that might be possible. Since they are fully modular its not even a big risk as spares are easily available.