I'm having a hard time finding a case I'd be happy with. This is frustrating. For about two years now you've been able to find tiny nettops with USB3+audio front ports and an integrated card reader and purchase everything but the RAM and HDD for well under $200. But if you want that plus a faster processor and an optical drive, heaven help you if you're trying to fit it into anything noticeably smaller than a full ATX case, and the situation hasn't gotten much better in the last few years.
Size: I may want to put this in a space that's 12"x10.5"x13.25" (WxHxD) (it does have space at the side and back for cooling). If I find something compelling enough I may get it even if it doesn't fit there, but that's about the I'm not going with a big honking 36L case like the BitFenix Prodigy. Why use a mini-ITX case that's almost as big as an ATX case? Anything that's much bigger than the 17L Antec NSK1380, a microATX case, starts to look doubtful.
Connectivity/Expandability: Essential to have front audio+USB3 ports, and space for an optical drive. I'd like an internal card reader. I can do the USB3+card reader with a 3.5" device, either in its own bay or using one full 5.25" bay, a slim drive, and something like this
. I want at least one expansion slot (low-profile is fine); two expansion slots is a plus (in case I get a double-slot card in the future or for things that attach to motherboard headers). The only hard drive I'll use is one 2.5" SSD.
PSU: my system won't need more than a 150W PSU, so the preference is for SFX or DC-DC + brick. For cases that take ATX or for cramped SFX cases I'll probably go PicoPSU
and grab one of these blanking plates/picopsu mounts
Quiet: Needs reasonable airflow, and no ZOMG 2X 60MM 4000RPM BLU LED 1NT4K3 FANZ 4 TEH G4M0RZ need apply.
Some examples of the many contenders I've looked at and not felt great about:
Lian Li PC-Q07: a bit taller than I'd like, but well built. WHY THE DEVIL DOESN'T IT HAVE FRONT AUDIO PORTS? But if I'd seen the recent newegg $40 deal in time, I'd probably have just bought it, grabbed a dremel, and tried to find a way to rectify that myself.
Apex MI-110: only aesthetics improved over the old MI-008, but meets a lot of my desiderata. It comes with a PSU that's awful enough I'd pay them $5 to not include it.
Thermaltake SD101: mostly a rebadged & facelifted IN-WIN BM639 +USB3. Included PSU has enough wattage and reasonably efficient. But mounting an optical drive gets in the way of airflow, and the PSU's 40mm fan, though it's been reviewed as quiet, seems likely to get noisy down the line esp. in a dusty room.
Antec NSK1380: I'm seriously considering hunting one of these old beasts down. Too bad Antec got complacent the last few years.