New Rackmount Server

I am building a new network for my home and putting in a rack so wanted to build a plex only server to stick in my rack and forget.

I have a Qnap NAS with 4 x 6TB hdd in which will still be connected on the network and this contains my media.

My current plex server is on my gaming pc which is a i7-6700k, 256gb Samsung 850 pro, 32gb DDR4 ram.

I am looking at either building a pc from scratch or buying like a Dell R710 used server.

I have 4k & 1080p movies and stream to 2 devices in the house and 2 people connect over the internet so need something to serve them without issues.

The only reason I was worried about the server option was if they can run SSD, noise level and also I have a few 4TB HDD I use for backup of my media and I believe the R710 does not allow drives over 2TB.

Any advice or suggestions welcome.

Thanks