First of all, maybe I should clarify that I currently own a mini-tower with plenty of empty drive bays that I could use, but I wish to find something way more compact. There's no set budget, but cheaper = better, unless convincing reasons exist to go with a more expensive option.
+ Sea Sonic SS-300TGW
+ Scythe Big Shuriken. An inexpensive combination with room for four low profile cards.
Nice find: nonetheless it has 1 drive bay and 60mm fans, does that suffice?
To the OP: don't you need some disk space on a server? In case, where do you want to place the drives in 10L or less? IMVHO it seems rather unpractical staying below a 15-20lt volume.
At any rate, here there's another small mATX enclosure: Cooler Master Elite 100
Both the suggested cases do match the size limitations.
However, my problem with both the Chenbro PC719 and the Cooler Master Elite 100 chassis is that they expect an integrated PSU with (small) fan. I'm deliberately trying to go the fanless PSU route, requiring only a large single fan for silently cooling both the CPU and generating airflow to cool the motherboard components inside the case. My envisioned server hardware uses less than 60W under load, so I don't need big PSU setups. A 90 or 120W brick with pico-PSU would suffice. I guess the 'fan-cooled' in my thread starter post is rather confusing; I meant to say that I don't require a fanless-CPU cooling setup, and would like to add a single fan to the system anyway (as to increase motherboard component lifetime). This fan could easily double as CPU cooler within the TDP I'm looking at (low-power Xeon chips).
The Elite 100 was actually on my original list, but like the iStarUSA S-0212-DT, it's currently out of stock on both newegg as well as amazon, making me doubt whether it's still in production.
I don't need to put any drives inside the server except for a small OS SSD. Storage is mounted over the network from an iSCSI target. All I need is room for a 2.5" SSD, and preferrably a single card expension slot for adding a NIC if needed.