Is it worth looking at second hand? If serious gamers are upgrading their rigs they may have some parts for sale that may still be good enough for your needs. I have an A8 in my tower, but I don't play games. My son has played a few on it and it coped.
Some form of backup has to be a priority. Automate it if possible. I have 100GB of Google drive and important files get synced to there immediately. You could get a Raspberry Pi with a USB drive and backup to that if you want more control.
Let us know how you get on.
The problem I have currently with performing online backups is I've only got 50GB of internet a month (shared between 3-4 people) so that isn't an option sadly.
I've got basically everything I need backed up I think in case doomsday hits.
Second hand is ok but I'd rather get a warranty and new parts for my own piece of mind.