haha there will always be better stuff coming later on (like sata ssd. there will be less changes in ddr3l ram except for price). just have fun with your current setup first

tbh, there are plenty of things that you can do with excess of ram.

yeah that space limit. however i think it should be ok if you use the 2.5" 1tb 7200rpm hdd from hgst. imo it's really better to go minimal, e.g. 1x ssd (os, software, games) + 1x hdd (downloads and storage). for long term storage it's better to use external storage or nas. in the case of disasters, you get lesser damage because of the limited space in the computer (less data affected hehe)