The iMac of current build with 256 ssd as plan A is going to replace Windows XP based 32Bit machine. On Windows the os and all installed software consume about 12GB on disc. I wonder if 256GB ssd in the new iMac will suffice if to assume there won't be any major increase in needs of installed applications and tasks the iMac will be used for. Let's assume eventually just a minor increase of software to be installed and to be used will take place. Let's keep the storage demand generated by documents and other big-stuff user data out of focus here. It is to be taken in considerations by other way. 4TB NAS is available in LAN for all big-stuff user data.