I have used successfully this setup:
Case: XION HTPC Series Micro ATX Slim Desktop Case - 1 x External 5.25" Drive Bays, 1 x Internal 3.5" Drive Bays, 4 x Exp Slots, 1 x 80mm Fan, 300W PSU
Motherboard: Gigabyte GA-78LMT-USB3 AM3+ AMD 760G + SB710 Motherboard - Micro ATX, Socket AM3+, AMD 760G + SB710 Chipset, Gigabit LAN, USB 3.0
CPU: AMD FD8320FRHKBOX FX-8320 Eight-Core 3.5GHz AM3+ Processor - AM3+, Eight-Core, 3.5GHz, 16MB, 125W, Unlocked
RAM: 4 X Kingston HyperX Fury Red 8GB Desktop Memory Module Kit - 1866MHz DDR3, CL10, DIMM - HX318C10FR/8. NOT ECC.
NIC: Startech Dual Port Gigabit Network Server Adapter NIC Card 2 Port used for Ceph Storage LAN
RAID CARD: LSI MegaRAID 9240-8i 8-port PCI-Express 6Gb/s RAID Controller IBM M1015 9220
HDD: 4 X 1 TB WD RED 2.5" Drives for Ceph in HDD Tray Connected to LSI MegaRaid card
SDD: 60 GB SDD 2.5" Drive into internal 3.5" drive bay for PVE System
HDD Tray: 4 Drive 2.5in Removable SAS SATA Mobile Rack Backplane into External 5.25" drive bay
I had a very good deal on RAM so I maxed out the MB to 32GB.
It is used for a home Cluster. With 5 CT and 2 KVM clients, it runs cool, quiet and stable on PVE 3.2 with kernel 2.6.32 and has been so since 3.2 officially came out.
I installed PVE 3.1 and then Dist-Upgraded to 3.2. It would not boot after install with 3.2 without 3.1 being there first. I have not upgraded to 3.3 yet based on what I heard on the forum. I will do it soon though.
Dual NIC configured for Round-Robin and used for Ceph LAN.
I have an older regular ATX Tower planned for a third node that was running PVE 2.X. With similar components (except ATX MB), it has 5 X 1TB WD RED HDD in a 5 in 3 internal SATA Rack Backplane to add to the Ceph storage. This will likely be using PVE 3.3 from scratch.
All a bit of an overkill for what I really need and use but I like to tinker and PVE makes it easy.
Serge