Wait a minute, that's a desktop right? I did a quick search for the specifications, and they are not unreasonable at all. The beauty of desktops is that you do not have to build a completely new PC when you need to upgrade!
Your most oudated parts are likely graphics card and CPU. You likely do not need more RAM. You should also check for power supply just in case.
So basically, identify a few games that you would like to play right now, then match your graphics card and CPU with those games to see which you have to buy replacements. Check PSU. At this point you most likely have some doughs left, which means you a.) did less work, b.) got more money left in your pocket, c.) have less hardware left behind, an d.) are hopefully happier as a result.