HP DL380 G7 with 10TB 2.5" drives & an Iomega PX4-300R NAS with 12 TB 3.5" drives. The HP runs all my 'arrs as well as does any coding work & acts as preliminary storage. Drives have cost me more than the server & NAS units.
Why did you opt for a setup with 2.5" disks? I ask because I just replaced my track server because the 2.5" are just more expensive than a server replacement plus 3.5" disks where I'm from (with 4x10tb).