Will these fans be good enough to cool my 1U server?

So, I have one of the chenbro servers that you can get pretty cheap on ebay for my VM server. This was fine when I had it in a rack in my utility room in my last house. I am now living with the in-laws across the country while house hunting in the new area and it sits on my desk. So, need to try and tame this thing. It is a 1U server with a pair of 8 core Sandy Bridge era chips and 128GB of RAM. These are cooled by a six or eight 40mm fans in the front of the chassis that scream. I want to try and put lower noise fans in, but not sure they have the grunt to keep things reasonably cool.

This is what I have in mind. NF-A4x20 PWM

I am not sure if I need the PWM ones or not. Need to see what the board supports.

I know any lower speed fan will cause higher temps. Most of the time the server is pretty low load except when doing Plex transcodes. So, that might get a bit iffy.