What am I building this ITX system for? I ask because I have several. Obviously the requirements are different depending on what you're building.
Main PC/games system (Q08): 1x2.5" SSD + 1x2.5" HDD, expansion slot for a 2.5-slot graphics card (would prefer 3 slot), optical drive (would prefer slim slot loading), large heatsink (AXP-140), full PSU
Main PC for office/internet (ISK310): 1x2.5"SSD + 1.2.5"HDD, no expansion slot, slot-loading optical drive
Main PC for the kids (ISK100): as above but without optical drive
NAS (Q08) - 1x2.5"SSD + 6x3.5"HDD (would prefer
, single expansion slot for RAID card, moderate HSF, optical drive not required, full PSU
HTPC-under-TV (dunno yet): 1x2.5"SSD, compact heatsink, small PSU (eg. pico-PSU), slim slot-loading optical drive
General HTPC (ISK100/ISK110/M350) - as above with without optical drive, VESA mountable
For the HTPCs on-board PSU and mSATA SSD would be nice but the motherboards I've found that support these aren't the cheapest.