Scythe heat sinks with push pins are a pain to install.
All of these cases are pretty tall and the optical drives don't overlap the CPU area. A mid size tower heat sink like the Xigmatek HDT-SD964
The Silverstone and Zalman have fan grill next to the CPU area and exhaust fans behind it.
The Lian Li only has exhaust fans, but it's the only one with some kind of hard drive decoupling, but It#s probably not too effective on the slim aluminum panels.
If you use quiet fans and decent fan controls 3.5" HDD will easily be the loudest part in your HTPC.