External HDD Rack Solution For More Storage?

Sometime last year I picked up a ThinkCentre SFF M910 for a very good price from a local shop. It’s a great little rig for running my Plex but I was hoping to expand it’s storage capabilities in order to also have it host network drives. Unfortunately the case itself only supports 2 HDDs and the board is one of those proprietary form factors that I don’t think I’d be able to move into a case with more space.

Any suggestions for a solution? I was thinking that maybe one of those external drive towers would be best but I’m not sure how they’d perform. I’d also likely need to buy a PCI-E card with more sata ports since the board only has one free (3 total).

Any advice is very welcome, thanks all :slight_smile: